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Carnegie Institution for Science1530 P Street, NW
Washington, DC 20005April 18-21, 2011
Teach EpidemiologyProfessional Development Workshop
Day3
2
Revised
Teach Epidemiology
Teach Epidemiology
3
4
A picture of the occurrence, the distribution, and the types of the diseases of mankind, in distinct epochs of time and at various
points on the earth's surface, and ... render an account of the relations of those diseases to the external condition.
(Hirsch, 1883)
What is epidemiology?
5
The science of the mass phenomena of infectious diseases, or as the natural history of infectious diseases ... an inductive science,
concerned not merely with describing the distribution of the disease, but fitting it into a consistent philosophy.
(Frost, 1927)
What is epidemiology?
6
Epidemiology may be defined as the study of the distribution of a disease or condition in a population and of the factors that
influence this distribution.
(Lilienfeld, 1957)
What is epidemiology?
7
Epidemiology is defined as the factors determining the frequency and distribution of disease in human populations. For many years the
word covered only and quite specifically, the study of the spread and decline of communicable disease in human populations and
the prophylaxis and control of those diseases ... the scope includes all disease, acute or chronic, physical or mental, communicable or non-
communicable.
(Epidemiology: A Guide to Teaching Methods, 1973)
What is epidemiology?
8
Epidemiology is a method of reasoning about disease that deals with the biologic inferences derived from observations of disease
phenomena in population groups.
(Lilienfeld, 1977)
What is epidemiology?
9
... the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to
the control of health problems.
(Gordis, 2009)
What is epidemiology?
10
14
Ecologic Study
Ecological Fallacy
An error in inference due to failure to distinguish between information
obtained from groups versus individuals. An association observed
between variables at a population level does not necessarily hold true
for individual members of these populations.
16
Outcome
+ -
+
-
Exposure a
c
b
d
Ecologic Study
17
18
19
20
21
22
Random Assignment
23
Random Assignment
24
Healthy PeopleHealthy People
E
Random Assignment
E
O
O
O
O
Blinding
Trial Investigators
Participants
Assessors
25
External Data Monitoring Board
Ethical Issues
26
Time Check
9:45 AM
27
28
Revised
Teach Epidemiology
Teach Epidemiology
29
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
30
Association Found Between Coffee and Pancreatic Cancer
Associated
Teach Epidemiology
31
What do we mean when we say that there is an association between two things?
Associated
Tied Related
Linked
Things that are associatedare linked in some way that makes them
turn up together.
Associated
Teach Epidemiology
32
Things that are associated are linked in some way that makes them turn up
together.
Associated
Teach Epidemiology
33
Suicide Higher in Areas with Guns
Smoking Linked to Youth Eating Disorders
Snacks Key to Kids’ TV- Linked Obesity: China Study
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Breakfast Each Day May Keep Colds Away
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
Pollution Linked with Birth Defects in US Study
Depressed Teens More Likely to Smoke
Associated
Teach Epidemiology
34
Epidemiologic studies that are concerned with characterizing the amount and distribution of
health and disease within a population.
Descriptive Epidemiology
Teach Epidemiology
35
Epidemiologic studies that are concerned with determinants of disease and the reasons for relatively high or low
frequencies of disease in specific population subgroups.
Analytical Epidemiology
Teach Epidemiology
36
Hypothesis
Formulating
Descriptive Epidemiology
Testing
Analytical Epidemiology
An unproven idea, based on observation or reasoning, that can
be supported or refuted through investigation
An educated guess
Hypothesis
Teach Epidemiology
37
Hypothesis:
Buprenorphine will stop heroin addicts from using heroin.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
38
PopulationTrial 1
Making Group Comparisons and Identifying Associations
39
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
Trial 1
Making Group Comparisons and Identifying Associations
40
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
21 Heroin Addicts Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
41
Bupe
Tested Positive for Heroin Total
10021 79
Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
Teach Epidemiology
42
When you can measure what you are speaking about, and express it in numbers,
you know something about it.
Lord Kelvin
But when you cannot measure it, when you cannot express it in
numbers, your knowledge is of a meager and unsatisfactory kind.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
43
A measure of how often an outcome occurs in a
defined population in a defined period of time. It consists of a
numerator and a denominator.
Risk
The numerator is the number of people in the population or
sample who experienced the outcome and the denominator is the total number of people in the
population or sample.
Population / Sample
Outcome
Denominator
Numerator
Making Group Comparisons and Identifying Associations
Teach Epidemiology
44
… the risk of a negative heroin test was 21 / 100 in a 10-week period
21 tested negative for
heroin 100 study subjects
Numerator
Denominator
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
45
A measure of how often an outcome occurs in a defined group of people
in a defined period of time.
The likelihood of an outcome occurring.
Risk / Rate
Making Group Comparisons and Identifying Associations
Teach Epidemiology
46
Trial 1
Bupe
Tested Positive for Heroin
10021 79
Tested Negative for Heroin
21
100or 21 %
Calculating Risk
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
47
Process of predicting from what is observed in a sample to what is true for the entire population.
Inference
Making Group Comparisons and Identifying Associations
Teach Epidemiology
48
Trial 1
What does this tell you about the hypothesis?
Buprenorphine will stop heroin addicts from using heroin.
InferenceProbe
Bupe
Tested Positive for Heroin
10021 79
Tested Negative for Heroin
21
100or 21 %
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
49
People who participate in a trial, but do not get the treatment.
People whose results are compared to the group that was treated.
Control Group
Making Group Comparisons and Identifying Associations
Teach Epidemiology
50
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Control Group
Extend and label the table to include a control group.
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
51
100?
100or ? %No Bupe
Control Group
Making Group Comparisons
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
52
100?
100or ? %No Bupe
Making Group Comparisons
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Exposure
Outcome / Disease
a b
c d
Risk of
Negative Heroin
Test
Total
Making Group Comparisons and Identifying Associations
Teach Epidemiology
53
21
100or 21 %
Total
1007921Bupe
100?
100or ? %No Bupe
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Making Group Comparisons and Identifying Associations
Teach Epidemiology
54
A cross-classification of data where categories of one variable
are presented in rows and categories of another variable
are presented in columns
The simplest contingency table is the 2x2 table.
Contingency Table
Making Group Comparisons and Identifying Associations
Teach Epidemiology
55
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
21 Heroin Addicts Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
56
Trial 2
Total
?
100? %
a b
c d
Bupe
Tested Negative for Heroin
Tested Positive for
Heroin
No Bupe 100
100?
100? %
Risk of
Negative Heroin
Test
Making Group Comparisons and Identifying Associations
Teach Epidemiology
57
E
Assigned
E
O
O
O
O
Making Group Comparisons and Identifying Associations
Volunteer Heroin Addicts
Teach Epidemiology
58
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Probe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Making Group Comparisons and Identifying Associations
Teach Epidemiology
59
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Making Group Comparisons and Identifying Associations
Teach Epidemiology
60
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
Making Group Comparisons and Identifying Associations
Teach Epidemiology
61
When you can measure what you are speaking about, and express it in numbers, you know something about it.
Lord Kelvin
But when you cannot measure it, when you cannot express it in
numbers, your knowledge is of a meager and unsatisfactory kind.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
62
The value obtained by dividing one quantity by another
Ratio
Making Group Comparisons and Identifying Associations
Teach Epidemiology
63
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Ratio: The value obtained by dividing one quantity by another
Risk Ratio: The ratio of two risks
1
Risk Ratio
Making Group Comparisons and Identifying Associations
Teach Epidemiology
64
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Ratio: The value obtained by dividing one quantity by another
Risk Ratio: The ratio of two risks
1
Risk Ratio
Create a formula
a
a + b
c
c + d
Making Group Comparisons and Identifying Associations
Teach Epidemiology
65
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
1
Risk Ratio
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
Relative Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
66
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
1
Risk RatioRelative Risk
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
The inference here is that there is no effect of Buprenorphine
Making Group Comparisons and Identifying Associations
Teach Epidemiology
67
Trial 3
?
100? %100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
?
100? %100 or
Making Group Comparisons and Identifying Associations
Teach Epidemiology
68
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
69
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
70
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
71
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
0.34
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
72
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
0.34
The heroin addicts who received Bupe were ___ times as likely to test negative for heroin as those who did not receive Bupe.
0.34
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
73
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
0.34
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population.
Trial 3
Making Group Comparisons and Identifying Associations
Teach Epidemiology
74
Trial 4
?
100? %100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
?
100? %100 or
Making Group Comparisons and Identifying Associations
Teach Epidemiology
75
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
76
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
77
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
3.5
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
78
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
3.5
The heroin addicts who received Bupe were ___ times as likely to test negative for heroin as those who did not receive Bupe.
3.5
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
79
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
3.5
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population.
Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
80
21
10021%21 79 100 orBupe
Trial 1
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
What do the results tell us about the hypothesis that Buprenorphine will stop heroin addicts from using heroin?
Nothing
Making Group Comparisons and Identifying Associations
Teach Epidemiology
81
Trial 1 Trial 2
Trial 3 Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
82
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
100
Making Group Comparisons and Identifying Associations
Teach Epidemiology
83
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
100
Making Group Comparisons and Identifying Associations
Teach Epidemiology
84
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
Making Group Comparisons and Identifying Associations
Teach Epidemiology
85
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
1
Bupe is not associated with having a negative test for heroin.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
86
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative test for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
Making Group Comparisons and Identifying Associations
Teach Epidemiology
87
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative test for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
1006 9490
or 6%6
100
Bupe is associated with having a negative test for heroin.
3.5
Making Group Comparisons and Identifying Associations
Teach Epidemiology
88
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative test for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
1006 9490
or 6%6
100
Bupe is associated with having a negative test for heroin.
3.5
Nothing
Compared to what?
Making Group Comparisons and Identifying Associations
Teach Epidemiology
89
Buprenorphine
Buprenorphine & Naloxone
Placebo
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Handout
90
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
91
92
Suicide Higher in Areas with Guns
Smoking Linked to Youth Eating Disorders
Snacks Key to Kids’ TV- Linked Obesity: China Study
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Breakfast Each Day May Keep Colds Away
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
Pollution Linked with Birth Defects in US Study
Depressed Teens More Likely to Smoke
In the News
93
Total
a b
dc
2 x 2 Table
Suicide Higher in Areas with Guns
94
Total
a b
dc
People who are exposed
a b
2 x 2 Table
Suicide Higher in Areas with Guns
Areas with Guns
No SuicideSuicide
Areas without Guns
95
a b
dc
2 x 2 Table
Total
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
96
a b
dc
2 x 2 Table
R-Rated Movies
TotalDrink & Smoke
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
No Drink & Smoke
No R-Rated
Movies
97
a b
dc
People who are exposed and have the outcome
a
2 x 2 Table
R-Rated Movies
TotalDrink & Smoke
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
No Drink & Smoke
No R-Rated
Movies
98
a b
dc
2 x 2 Table
Family Meals Are Good for Mental Health
Total
99
a b
dc
2 x 2 Table
Family Meals Are Good for Mental Health
Family Meals
TotalMental Health
No Mental Health
No Family
Meals
100
a b
dc
People who are not exposed and do not have the outcome
d
2 x 2 Table
Family Meals Are Good for Mental Health
Family Meals
TotalMental Health
No Mental Health
No Family
Meals
101
a b
dc
2 x 2 Table
Study Links Iron Deficiency to Math Scores
Total
102
a b
dc
2 x 2 Table
Study Links Iron Deficiency to Math Scores
Iron Deficiency
Poor Math
Scores
No Iron
Deficiency
Good Math
Scores Total
103
a b
dc
People who do not have the outcome and are not exposed
d
2 x 2 Table
Study Links Iron Deficiency to Math Scores
Iron Deficiency
Poor Math
Scores
No Iron
Deficiency
Good Math
Scores Total
104
a b
dc
2 x 2 Table
Pollution Linked with Birth Defects in US Study
Total
105
a b
dc
2 x 2 Table
Pollution Linked with Birth Defects in US Study
Pollution
Birth Defects
No Pollution
No Birth
Defects Total
106
a b
dc
People who are not exposed
dc
2 x 2 Table
Pollution Linked with Birth Defects in US Study
Pollution
Birth Defects
No Pollution
No Birth
Defects Total
107
a b
dc
2 x 2 Table
Depressed Teens More Likely to Smoke
Total
108
a b
dc
People who do not have the outcome
d
b
2 x 2 Table
Depressed Teens More Likely to Smoke
Depression
Smoke
No Depression
No Smoke Total
109
a b
dc
2 x 2 Table
Smoking Linked to Youth Eating Disorders
Total
110
a b
dc
2 x 2 Table
Smoking Linked to Youth Eating Disorders
Smoke
Eating Disorders
No Smoke
No Eating
Disorders Total
111
a b
dc
People who are exposed and do not have the outcome
b
2 x 2 Table
Smoking Linked to Youth Eating Disorders
Smoke
Eating Disorders
No Smoke
No Eating
Disorders Total
112
a b
dc
2 x 2 Table
Total
Study Links Spanking to Aggression
113
a b
dc
People who have the outcome
a
c
2 x 2 Table
Study Links Spanking to Aggression
Spanking
Aggression
No Spanking
TotalNo
Aggression
114
a b
dc
2 x 2 Table
Total
Snacks Key to Kids’ TV-Linked Obesity – China Study
115
a b
dc
2 x 2 Table
Snacks Key to Kids’ TV-Linked Obesity – China Study
Snacks
Obesity
No Snacks
No Obesity Total
People who are not exposed and have the outcome
c
116
117
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
118
Laboratory
Teach Epidemiology
Making Group Comparisons and Identifying Associations
119
Laboratory
Teach Epidemiology
Making Group Comparisons and Identifying Associations
120
Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an
outcome.
Natural Experiment
Teach Epidemiology
Making Group Comparisons and Identifying Associations
121
An epidemiologic study of a natural experiment in which the investigator is not involved in the intervention other than to record, classify, count,
and statistically analyze results.
Observational Study
Teach Epidemiology
Making Group Comparisons and Identifying Associations
122
An epidemiologic experiment in which subjects are assigned into groups to receive or not receive
a hypothesized beneficial intervention.
Controlled Trial
Teach Epidemiology
Making Group Comparisons and Identifying Associations
123
Buprenorphine
Buprenorphine will stop heroin addicts from using heroin.
Teach Epidemiology
Making Group Comparisons and Identifying Associations
124
Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an
outcome.
Observational Study of a Natural Experiment
Epidemiologic studies of natural experiments in which the investigator is not involved in the
intervention other than to record, classify, count, and statistically analyze results.
Teach Epidemiology
Making Group Comparisons and Identifying Associations
125
Making Group Comparisons and Identifying Associations
Teach Epidemiology
126
Making Group Comparisons and Identifying Associations
Teach Epidemiology
127
Stephen Jay Gould (survivor of abdominal mesothelioma)
Absolutely nothing in the available arsenal of anti-emetics worked at all. I was miserable and came to dread the frequent treatments with an almost perverse intensity. I had heard that marijuana often worked well against nausea. I was reluctant to try it because I had never smoked any substance habitually (and didn’t even know how to inhale). Moreover, I had tried marijuana twice (in the 1960s) … and had hated it …. Marijuana worked like a charm …. The sheer bliss of not experiencing nausea - and not having to fear it for all the days intervening between treatments - was the greatest boost I received in all my year of treatment, and surely the most important effect upon my eventual cure.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
128
A particular or detached incident or fact of an interesting nature; a biographical incident or
fragment; a single passage of private life.
Anecdote
Making Group Comparisons and Identifying Associations
Teach Epidemiology
129
Science
Transforming Anecdote to Science
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Anecdote
130
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Controlled Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Cohort Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Case-Control Study
-
DZ
DZ
E
E
E
E
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Cross-Sectional Study
-
E
E
DZ
DZ
Making Group Comparisons and Identifying Associations
Teach Epidemiology
131
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Controlled Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Cohort Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Case-Control Study
-
DZ
DZ
E
E
E
E
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Cross-Sectional Study
-
E
E
DZ
DZ
d
b
c
a
Making Group Comparisons and Identifying Associations
Teach Epidemiology
The goal of every epidemiological study is to harvest valid and precise information about the
relationship between an exposure and a disease in a population.
The various study designs merely represent different ways of harvesting this information.
Essentials in Epidemiology in Public HealthAnn Aschengrau and George R. Seage III
Making Group Comparisons and Identifying Associations
Teach Epidemiology
133
134
Ms. Wilson
After-School, Make-Up Homework Hall
135
Talking too much on a cell phone causes students not to do their homework.
a
c
b
d
Label the 2x2 Table
136
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
137
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
Place the data into the 2x2 Table
138
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
139
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
Which of the following statements can be made based on the above data:
A: 15 of 20 students, who did not do their homework, had cell phones. B: 15 of 20 students, who had cell phones, did not do their homework.
140
Breast Implants
No Breast
Implants
No Connective Tissue Disease
3 1,180 1,183
513 85,805 86,318
Cohort Study – The Nurses’ Health Study (1976)
Which of the following statements can be made based on the above data:
A: 15 of 20 students, who did not do their homework, had cell phones. B: 15 of 20 students, who had cell phones, did not do their homework.
TotalConnective
Tissue Disease
Risk
141
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
Which of the following statements can be made based on the above data:
A: 15 of 20 students, who did not do their homework, had cell phones. B: 15 of 20 students, who had cell phones, did not do their homework.
RiskX
Odds
142
Odds
A ratio of the probability of occurrence of an event to that of its nonoccurrence.
Talking too much on a cell phone causes students not to do their homework.
143
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
15
5
Which of the following statements can be made based on the above data:
A: 15 of 20 students, who did not do their homework, had cell phones. B: 15 of 20 students, who had cell phones, did not do their homework.
A ratio of the probability of occurrence
of an event to that of its nonoccurrence.
15 to 5 or 3 to 1
Odds
Talking too much on a cell phone causes students not to do their homework.
20
144
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
15
5
Which of the following statements can be made based on the above data:
A: 15 of 20 students, who did not do their homework, had cell phones. B: 15 of 20 students, who had cell phones, did not do their homework.
Talking too much on a cell phone causes students not to do their homework.
20
Nothing
A ratio of the probability of occurrence
of an event to that of its nonoccurrence.
15 to 5 or 3 to 1
OddsCompared to what?
145
CompareDivideCount
Talking too much on a cell phone causes students not to do their homework.
146
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
15
5
Which of the following statements can be made based on the above data:
A: 15 of 20 students, who did not do their homework, had cell phones. B: 15 of 20 students, who had cell phones, did not do their homework.
Talking too much on a cell phone causes students not to do their homework.
20
Nothing
A ratio of the probability of occurrence
of an event to that of its nonoccurrence.
15 to 5 or 3 to 1
OddsCompared to what?
What did Ms. Wilson do?
147
Talking too much on a cell phone causes students not to do their homework.
What did Ms. Wilson do?
148
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
10
30
403 to 1
10 to 30 or 1
to 3
Place the data into the 2x2
Table
149
What mathematical computation would allow them to complete the statement:
The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
10
30
403 to 1
10 to 30 or 1
to 3
What mathematical computation would allow them to complete the statement:
The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.150
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
10
30
403 to 1
3 / 1 = 3 1 / 3 = .333 / .33 = 9
9
10 to 30 or 1
to 3
151
Odds Ratio
Ratio of odds in favor of exposure among cases to the odds in favor of exposure among controls.
Talking too much on a cell phone causes students not to do their homework.
Relative Odds
152
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
35
5
40
Odds Ratio
What mathematical computation would allow them to complete the statement:
The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.
.43
153
a
c
b
dDid Not
Have Cell Phone
Did Not Do Homework
Did Homework
Had Cell Phone
Total
Talking too much on a cell phone causes students not to do their homework.
15
5
20
30
10
40
Odds Ratio
What mathematical computation would allow them to complete the statement:
The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.
1
154
155
Arthur Herbst, et al. “Adenocarcinoma of the Vagina,” New England Journal of Medicine, 284:16, 1971, 878-881
Case-Control Study
156
Case-Control Study
157
Case-Control Study
158
Case-Control Study
159
Case-Control Study
160
Case-Control Study
161
Case-Control Study
162
DZ
X
DZ
_
X
_
DZ
8
1
7
Case-Control Study
163
DZ
X
DZ
_
X
_
DZ
8
5
3
Case-Control Study
164
DZ
X
DZ
_
X
_
DZ
8
2
6
Case-Control Study
165
DZ
X
DZ
_
X
_
DZ
8
1
7
Case-Control Study
166
DZ
X
DZ
_
X
_
DZ
8
5
3
Case-Control Study
167
DZ
X
DZ
_
X
_
DZ
8
7
1
Case-Control Study
168
Case-Control Study
169
DZ
X
DZ
_
X
_
DZ
8 32
1
7 21
11
Case-Control Study
170
DZ
X
DZ
_
X
_
DZ
8 32
5
3 1
31
Case-Control Study
171
DZ
X
DZ
_
X
_
DZ
8 32
2
6 5
27
Case-Control Study
172
DZ
X
DZ
_
X
_
DZ
8 32
1
7 0
32
Case-Control Study
173
DZ
X
DZ
_
X
_
DZ
8 32
5
3 3
29
Case-Control Study
174
DZ
X
DZ
_
X
_
DZ
8 32
7
1 4
28
Case-Control Study
175
Case-Control Study
Case-Control Study
177
Authentic Assessment
Teach Epidemiology
Epi – Grades 6-12
• Are realistic; simulate the way a person’s understanding is tested in the real world
•Require judgment and innovation to address an unstructured problem, rather than following a set routine
• Ask students to “do” the subject rather than simply recall what was taught
•Replicate the context in which a person would be tested at work, in the community, or at home
• Are messy and murky
• Require a repertoire of knowledge and skill to be used efficiently and effectively
• Allow opportunities for rehearsal, practice, consultation, feedback, and refinement
179
Epi Challenge
http://www.teachepidemiology.org/viewSO1.php
180
Epi Challenge
http://www.teachepidemiology.org/viewSO2.php
Think Like an Epidemiologist ChallengeNew Jersey Science Olympiad, March 15, 2011
Thank you for competing in the 3rd Think Like an Epidemiologist Challenge.
You worked with others, developed epidemiologic knowledge and skills, and used judgment and innovation to actually "do" epidemiology under
pressure.
We hope you enjoyed the challenge.
NameSchool
Teach Epidemiology
Robert Wood Johnson Foundation
Detectives in the
Classroom
Special thanks to the Epidemiology Section of the American Public Health Association for allowing us to distribute their Section pins to the student participants in the 2011 Think Like an Epidemiologist Challenge.
202
Time Check
10:45 AM
203
204
Revised
Teach Epidemiology
Teach Epidemiology
205
Time Check
11:00 AM
206
The Journey
The Journey
Detectives in the Classroom - Investigation 2-6: The Journey
The Journey from Exposure to Disease
Detectives in the Classroom - Investigation 2-6: The Journey
Analogy
Detectives in the Classroom - Investigation 2-6: The Journey
Epi Talk
Study Design Epi Talk
Detectives in the Classroom - Investigation 2-6: The Journey
Procedures and methods, established beforehand, that are followed by the investigator conducting the study.
Timing
When are the passengers identified as exposed or unexposed?
E
When are the passengers identified as sick or not sick?
DZ
Timing
When does the epidemiologist start to observe the journey?
-
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E DZ
Label the Train Tracks
-
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Study Design:
E DZ
Label the Train Tracks
-
Detectives in the Classroom - Investigation 2-6: The Journey
Controlled Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Controlled
Trial
Flow Diagram
Flow Diagram
Detectives in the Classroom - Investigation 2-6: The Journey
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Study Design:
Label the Train Tracks
Detectives in the Classroom - Investigation 2-6: The Journey
Cohort Study
Cohort Study
Just as in the controlled trial, the epidemiologist is also on the train during the entire journey. But there is an important difference. The epidemiologist is not telling passengers what to do. Rather, the epidemiologist is just observing them and counting. Passengers are not being told to have or not have an exposure, they are just living their normal lives. The epidemiologist, on the ride for the whole journey, just keeps observing everyone’s exposures and whether or not they develop the disease during the journey.
Label the Train Tracks
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E DZ
Label the Train Tracks
-
Detectives in the Classroom - Investigation 2-6: The Journey
Study Design: Cohort Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Cohort
Study
Flow Diagram
Flow Diagram
Detectives in the Classroom - Investigation 2-6: The Journey
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Cohort
Study
Flow Diagram
Flow Diagram
Detectives in the Classroom - Investigation 2-6: The Journey
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Controlled
Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
Cohort
Study
Flow Diagram
Flow Diagram
Detectives in the Classroom - Investigation 2-6: The Journey
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Controlled
Trial
Random Assignment
Review
Observational StudiesEpi Talk
Detectives in the Classroom - Investigation 2-6: The Journey
Epidemiologic studies of natural experiments in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results.
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Label the Train Tracks
Detectives in the Classroom - Investigation 2-6: The Journey
Study Design: Case-Control Study
The epidemiologist is not on the journey. Rather, the epidemiologist is waiting at the train station at the end of the journey. As passengers get off the train, the epidemiologist selects sick passengers for the case group and selects passengers who are similar but not sick for the control group. The epidemiologist then asks each person in the case group and control group questions about their exposures during the train ride. The epidemiologist relies on passengers’ memories of their exposures that occurred during the train ride.
Label the Train Tracks
Case-Control Study
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E
DZ
Label the Train Tracks
-
Detectives in the Classroom - Investigation 2-6: The Journey
Study Design: Case-Control Study
Case-Control
Study
Observational
Study
Flow Diagram
Flow Diagram
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
DZ
-
DZ
E
E
E
E
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Label the Train Tracks
Detectives in the Classroom - Investigation 2-6: The Journey
Study Design: Cross-Sectional Study
The epidemiologist, who has not been on the journey, stops the train somewhere during the trip (kind of like a train robbery) and takes a “snapshot” of all the passengers by asking them whether or not they have the exposure and whether or not they have the disease. Then the epidemiologist leaves the train and goes home to analyze the data from that particular day. The journey continues without the epidemiologist.
Label the Train Tracks
Cross-Sectional Study
Detectives in the Classroom - Investigation 2-6: The Journey
EDZ
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Label the Train Tracks
-
Detectives in the Classroom - Investigation 2-6: The Journey
Study Design: Cross-Sectional Study
Cross-Sectional
Study
Observational
Study
Flow Diagram
Flow Diagram
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
E
E
-
DZ
DZ
Detectives in the Classroom - Investigation 2-6: The Journey
Epi Talk
Controlled TrialEpi Talk
Detectives in the Classroom - Investigation 2-6: The Journey
An epidemiologic experiment in which subjects are assigned into groups to receive or not receive a hypothesized beneficial intervention.
Epi Talk
Cohort StudyEpi Talk
Detectives in the Classroom - Investigation 2-6: The Journey
An analytical epidemiological study design in which the investigator selects a group of exposed individuals and a group of unexposed individuals and follows both groups to compare the frequency with which the disease occurs in each group.
Epi Talk
Case-Control StudyEpi Talk
Detectives in the Classroom - Investigation 2-6: The Journey
An analytical epidemiological study design in which the investigator selects a group of individuals with a disease (cases) and a group of similar individuals without the disease (controls) and compares the frequency with which an exposure occurred in the cases versus the controls.
Epi Talk
Cross-Sectional StudyEpi Talk
Detectives in the Classroom - Investigation 2-6: The Journey
An analytical epidemiological study design in which the investigator selects a group of individuals and determines the presence or absence of a disease and the presence or absence of an exposure at the same time.
234
Epi Teams
Detectives in the Classroom - Investigation 2-6: The Journey
What’s My Design?
Detectives in the Classroom - Investigation 2-6: The Journey
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Controlled Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Cohort Study
Epi Team
Challenge
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-
DZ
DZ
E
E
E
E
Case-Control Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-
E
E
DZ
Cross-Sectional Study
DZ
Controlled Trial
Epidemiologist is involved during the entire time from exposure and disease.
Assign treatment and control groups.
Follow through time and compare risk of disease in treatment group with risk of disease in control group.
Give exposure to treatment group, but not control group.
What’s My Design?
Detectives in the Classroom - Investigation 2-6: The Journey
Observational
Study
Flow Diagram
Flow Diagram
-
DZ
DZ
E
E
E
E
Detectives in the Classroom - Investigation 2-6: The Journey
Case-Control Study
Observational
Study
Detectives in the Classroom - Investigation 2-6: The Journey
What’s My Design?
Cohort, Case-Control, and Cross-Sectional Study
CDC
Investigation 2-6 has ended.
The Journey
Detectives in the Classroom - Investigation 2-6: The Journey
241
Epi Team Challenge
Epi Team ChallengeDetectives in the Classroom - Investigation 2-7: Epi Team Challenge
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Controlled Trial
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Cohort Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-
DZ
DZ
E
E
E
E
Case-Control Study
Time
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-
E
E
DZ
Cross-Sectional Study
DZ
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist is involved during the entire time from exposure to disease.
Assign treatment and control groups.
Follow through time and compare risk of disease in treatment group with risk of disease in control group.
Give exposure to treatment group, but not control group.
What’s My Design?
Practice Clue
Trial
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Assign treatment and control groups.
What’s My Design?
Clue 1
Begin Epi Team Challenge
Trial
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Observational
Study
Flow Diagram
DZ
-
DZ
E
E
E
E
Clue 2
Case-Control Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Observational
Study
Flow Diagram
Clue 3
What’s My Design?
Cohort, Case-Control, and Cross-Sectional Studies
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Follow through time and compare risk of disease in exposed group with risk of disease in the unexposed group.
Clue 4
Trial and Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Follow through time and compare risk of disease in treatment group with risk of disease in control group.
Give exposure to treatment group, but not control group.
Clue 5
Trial
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist is involved during the entire time from exposure to disease.
Clue 6
Trial and Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Select a group of people with disease and a similar group of people without disease.
Clue 7
Case-Control Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Healthy People
Flow Diagram
-
Healthy People
E
E
Random Assignment
Non-Observational
Study
Clue 8
Trial
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Observational
Study
Flow Diagram
E
E
-
DZ
DZClue 9
Cross Sectional Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Compare percent of exposed people in the two groups.
Clue 10
Case-Control Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Healthy People
Flow Diagram
-
Healthy People
E
E
DZ
DZ
DZ
DZRandom
Assignment
Clue 11
Trial
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Flow Diagram
Clue 12
Cross Sectional Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Flow Diagram
DZ
DZ
DZ
DZObservational
Study
Clue 13
Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Ask each person about both exposure and disease at that point in time.
What’s My Design?
Clue 14
Cross Sectional Study
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Ask both groups about their exposures in the past.
What’s My Design?
Clue 15
Case-Control Study
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Healthy People
Flow Diagram
-
Healthy People
Random Assignment
Clue 16
Trial
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Disease risk in exposed group is compared to disease risk in unexposed group.
Clue 17
Trial, Cohort Study, and Cross Sectional Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Flow Diagram
E
E
-
DZ
DZClue 18
Cross Sectional Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Select a healthy study sample.
Clue 19
Trial (?) and Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Observe who has and has not been exposed.
Clue 20
Cohort and Cross-Sectional Studies
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Clue 21
Give exposure to treatment group, but not control group.
Trial
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Healthy People
Flow Diagram
-
Healthy People
E
EObservational
Study
Clue 22
Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist is involved after disease has occurred and relies on subjects’ memories
to gather information about exposure.
Clue 23
Case-Control Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Select a study sample.
Clue 24
Trial, Cohort, Case-Control, and Cross Sectional Studies
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Healthy People
Flow Diagram
-
Healthy People
E
E
DZ
DZ
DZ
DZObservational
Study
Clue 25
Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist gathers data only at that one point in time.
Clue 26
Cross Sectional Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Flow Diagram
DZ
DZ
DZ
DZ
Clue 27
Trial and Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Follow through time and compare risk of disease in exposed group to risk of disease in unexposed group.
Clue 28
Trial and Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist is involved during the entire time from exposure to disease.
Clue 29
Trial and Cohort Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Flow Diagram
E
E
DZ
DZClue 30
Cross Sectional Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Flow Diagram
DZ
-
DZ
Clue 31
Case-Control Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Ask each person about both exposure and disease at that point in time.
Epidemiologist gathers data only at that one point in time.
Disease risk in exposed group is compared to disease risk in unexposed group.
Select a study sample.
Clue 32
Cross Sectional Study
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist is involved after disease has occurred and relies on subjects’ memories to gather information
about exposure.
Select a group of people with disease and a similar group of people without disease.
Compare percent of exposed people in the two groups.
Ask both groups about their exposures in the past.
Case-Control Study
Clue 33
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist is involved during the entire time from exposure to disease.
Select a healthy study sample.
Follow through time and compare risk of disease in exposed group to risk of disease in unexposed group.
Observe who has and has not been exposed.
Cohort Study
Clue 34
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Epidemiologist is involved during the entire time from exposure to disease.
Assign treatment and control groups.
Follow through time and compare risk of disease in treatment group with risk of disease in control group.
Give exposure to treatment group, but not control group.
Trial
Clue 35
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
End Epi Team Challenge
What’s My Design?
Detectives in the Classroom - Investigation 2-7: Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Which Design
Is Best?
Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Epi Team ChallengeEpi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Cross-Sectional
CohortCase-
Control Controlled
Trial
Epi Team ChallengeEpi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Which study design is the fastest?
Epi Team ChallengeEpi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Time Consuming
Which study designs are the most time consuming?
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Most Scientifically Sound
Which study design is the most scientifically sound?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Most Scientifically Sound
Can Study Rare Diseases
Which study design is best for studying rare diseases?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Most Scientifically Sound
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Which study designs do not identify the time order of exposure and disease?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Which study design gives the least confidence in findings?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Which study design provides the best measure of exposure?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Most Accurate Observational Study
Which study design is the most accurate observational study?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Least Expensive
Most Accurate Observational Study
Which study design is the least expensive?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Least Expensive
Unethical for Harmful Exposures
Most Accurate Observational Study
Which study design would be unethical for harmful
exposures?
Time Consuming
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Least Expensive
Good Measure of Exposure
Which study design provides a good measure of exposure?
Most Accurate Observational Study
Time ConsumingUnethical for Harmful exposures
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Least Expensive
Most Expensive
Most Expensive
Most Accurate Observational Study
Which study designs are the most expensive?
Good Measure of Exposure
Time ConsumingUnethical for Harmful exposures
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Least Expensive
Relatively Less Expensive and Relatively Fast
Most Accurate Observational Study
Which study design is relatively less expensive and relatively fast?
Time ConsumingUnethical for Harmful exposures
Most Expensive
Most ExpensiveGood Measure of Exposure
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Least Confidence in Findings
Most Scientifically Sound
Best Measure of Exposure
Possible Time-Order Confusion
Possible Time-Order Confusion
Can Study Rare Diseases
Least Expensive
Relatively Less Expensive and Relatively Fast
Possible Error in Recalling Past Exposures
Most Accurate Observational Study
Which study design creates the possibility of error in recalling past exposures?
Time ConsumingUnethical for Harmful exposures
Most Expensive
Most ExpensiveGood Measure of Exposure
Epi Team Challenge
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
Cross-Sectional Study
Case-Control Study
Cohort Study
Trial
Main WeaknessesMain StrengthsStudy Designs
1 5
62
3 7
84
Fastest
Time Consuming
Most Scientifically Sound
Best Measure of Exposure
Can Study Rare Diseases
Least Expensive
Relatively Less Expensive and Relatively Fast
Possible Error in Recalling Exposures
Most Accurate Observational Study
Which Design Is Best?
Which Design Is Best?
Time Consuming
Unethical for Harmful exposuresMost Expensive
Most Expensive
Possible Time-Order Confusion
Possible Time-Order Confusion
Least Confidence in Findings
Good Measure of Exposure
It depends ….
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
It depends on ….
• Regulations
• Time urgency
• How much is known about the association
• Money
• Whether the exposure is believed to be beneficial
Detectives in the Classroom - Investigation 2-8: Which Design Is Best?
DZ DZ
E
E
db
ca
Flow Diagram 2x2 Table
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
&
“fit”
Designs, Diagrams, and Tables
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
DZ DZ
E
Ea
2x2 Table
Where do these people “fit” in the 2x2 table?
Flow Diagram
Controlled Trial
Healthy PeopleHealthy People
E
E
DZ
DZ
DZ
DZ
Random Assignment
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
Eb
Flow Diagram 2x2 Table
Healthy PeopleHealthy People
E
E
DZ
DZ
DZ
DZ
Random Assignment
Where do these people “fit” in the 2x2 table?
Controlled Trial
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E
c
Flow Diagram 2x2 TableFlow Diagram
Healthy PeopleHealthy People
E
E
DZ
DZ
DZ
DZ
Random Assignment
Where do these people “fit” in the 2x2 table?
Controlled Trial
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E
d
2x2 TableFlow Diagram
Healthy PeopleHealthy People
E
E
DZ
DZ
DZ
DZ
Random Assignment
Where do these people “fit” in the 2x2 table?
Controlled Trial
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E
c
Flow Diagram 2x2 Table
Where are these people in the flow diagram?
Cohort Study
Healthy PeopleHealthy People
E
E
DZ
DZ
DZ
DZ
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
Ea
2x2 Table
Where are these people in the flow diagram?
Flow Diagram
Cohort Study
Healthy People
E
E
DZ
DZ
DZ
DZ
Healthy People
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E
d
Flow Diagram 2x2 Table
Where are these people in the flow diagram?
Cohort Study
Healthy People
E
E
DZ
DZ
DZ
DZ
Healthy People
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
Eb
Flow Diagram 2x2 Table
Where are these people in the flow diagram?
Cohort Study
Healthy People
E
E
DZ
DZ
DZ
DZ
Healthy People
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
Ea
Where do these
people go in the
2x2 table?
2x2 Table Flow Diagram
Case-Control Study
DZ
DZ
E
E
E
E
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E
c
Where do these
people go in the
2x2 table?
Flow Diagram2x2 Table
Case-Control Study
DZ
DZ
E
E
E
E
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
Flow Diagram
DZ DZ
E
E b
2x2 Table
Where do these
people go in the
2x2 table?
Case-Control Study
DZ
DZ
E
E
E
E
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
Flow Diagram
DZ DZ
E
E
d
2x2 Table
Where do these
people go in the
2x2 table?
Case-Control Study
DZ
DZ
E
E
E
E
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E aFlow Diagram
2x2 Table
Where do these
people go in the
2x2 table?
Cross-Sectional Study
E
E
DZ
DZ
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E
c
Flow Diagram
2x2 Table
Where do these
people go in the
2x2 table?
Cross-Sectional Study
E
E
DZ
DZ
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
E
d
Flow Diagram
2x2 Table
Where do these
people go in the
2x2 table?
Cross-Sectional Study
E
E
DZ
DZ
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
DZ DZ
E
Eb
Flow Diagram
2x2 Table
Where do these
people go in the
2x2 table?
Cross-Sectional Study
E
E
DZ
DZ
Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables
319
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
The goal of every epidemiological study is to harvest valid and precise information about the
relationship between an exposure and a disease in a population.
The various study designs merely represent different ways of harvesting this information.
Essentials in Epidemiology in Public HealthAnn Aschengrau and George R. Seage III
Making Group Comparisons and Identifying Associations
Teach Epidemiology
321
322
Revised
Teach Epidemiology
Teach Epidemiology
Teach Epidemiology Workshop—Day 3Diane Marie M St. George, PhDUniversity of MD School of MedicineDept of Epidemiology and Public Health
EU7: One possible explanation for EU7: One possible explanation for finding an association is that the finding an association is that the exposure causes the outcome. exposure causes the outcome. Because studies are complicated by Because studies are complicated by factors not controlled by the observer, factors not controlled by the observer, other explanations also must be other explanations also must be considered, including confounding, considered, including confounding, chance, and bias.chance, and bias.
EU8: Judgments about whether an exposure EU8: Judgments about whether an exposure causes a disease are developed by causes a disease are developed by examining a body of epidemiologic examining a body of epidemiologic evidence, as well as evidence from other evidence, as well as evidence from other scientific disciplines.scientific disciplines.
EU9: While a given exposure may be EU9: While a given exposure may be necessary to cause an outcome, the necessary to cause an outcome, the presence of a single factor is seldom presence of a single factor is seldom sufficient. Most outcomes are caused sufficient. Most outcomes are caused by a combination of exposures that may by a combination of exposures that may include genetic make-up, behaviors, include genetic make-up, behaviors, social, economic, and cultural factors social, economic, and cultural factors and the environment. and the environment.
Reasons for associations
Confounding Bias Reverse causality Sampling error (chance) Causation
Confounding in our lives
MAP tests measure academic growth over time, independent of grade level or age.
Age- and gender-specific growth charts Age-adjusted rates of… Rates of lung cancer adjusted for smoking Computer exposure may cause illness
(absence), but it actually may just be the football game
Osteoporosis risk is higher among women who live alone than among women who live with others.
Confounding
Confounding is an alternate explanation for an observed association of interest.
Number of persons in the
homeOsteoporosis
Age
Confounding
Confounding is an alternate explanation for an observed association of interest.
Exposure Outcome
Confounder
Controlling confounding
Study design phaseMatchingRestrictionRandom assignment
Study analysis phaseStratificationStatistical adjustment
Reasons for associations
Confounding Bias Reverse causality Sampling error (chance) Causation
Bias
Errors are mistakes that are:randomly distributednot expected to impact the MA less modifiable
Biases are mistakes that are:not randomly distributedmay impact the MAmore modifiable
Types of bias
Selection biasThe process for selecting/keeping subjects
causes mistakes Information bias
The process for collecting information from the subjects causes mistakes
Selection bias People who are working are likely to be
healthier than non-workers People who participate in a study may
be different from people who do not People who drop out of a study may be
different from those who stay in the study
Hospital controls may not represent the source population for the cases
Information bias
Misclassification, e.g. non-exposed as exposed or cases as controls
Cases are more likely than controls to recall past exposures
Interviewers probe cases more than controls (exposed more than unexposed)
Birth defects and diet
In a study of birth defects, mothers of children with and without infantile cataracts are asked about dietary habits during pregnancy.
Pesticides and cancer mortality
In a study of the relationship between home pesticide use and cancer mortality, controls are asked about pesticide use and family members are asked about their loved ones’ usage patterns.
Minimize bias
Can only be done in the planning and implementation phase
Standardized processes for data collection Masking Clear, comprehensive case definitions Incentives for participation/retention
Reasons for associations
Confounding Bias Reverse causality Sampling error (chance) Causation
Reverse causality
Suspected disease actually precedes suspected cause
Pre-clinical disease Exposure DiseaseFor example: Memory deficits Reading
cessation Alzheimer’s Cross-sectional study
For example: Sexual activity/Marijuana
Minimize effect of reverse causality
Done in the planning and implementation phase of a study
Pick study designs in which exposure is measured before disease onset
Assess disease status with as much accuracy as possible
Reasons for associations
Confounding Bias Reverse causality Sampling error (chance) Causation
Sampling error/chance
E and D are associated in a sample, but not in the population from which the sample was drawn.
RR in the populationRR in the population
D+D+ D-D-
E+E+ 5050 5050 100100
E-E- 5050 5050 100100
100100 100100 200200
RR = (24 / 718) / (281 / 8566) = 1.0
RR in sample 1RR in sample 1
D+D+ D-D-
E+E+ 2525 2525 5050
E-E- 2525 2525 5050
5050 5050 100100
RR = (24 / 718) / (281 / 8566) = 1.0
RR in sample 2RR in sample 2
D+D+ D-D-
E+E+ 4545 55 5050
E-E- 1515 3535 5050
5050 5050 100100
RR = (24 / 718) / (281 / 8566) = 1.0
RR in sample 3RR in sample 3
D+D+ D-D-
E+E+ 2020 3030 5050
E-E- 3030 2020 5050
5050 5050 100100
RR = (24 / 718) / (281 / 8566) = 1.0
Minimize sampling error (chance)
Random Selection
351
Time Check
12:30 PM
352
353
Revised
Teach Epidemiology
Teach Epidemiology
354
Time Check
1:30 PM
355
356
Revised
Teach Epidemiology
Teach Epidemiology
357
Time Check
2:00 PM
358
359
Revised
Teach Epidemiology
Teach Epidemiology
360
361Teach Epidemiology
Enduring Epidemiological Understandings
362
Suicide Higher in Areas with Guns
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
Pollution Linked with Birth Defects in US Study
Ties, Links, Relationships, and Associations
Snacks Key to Kids’ TV- Linked Obesity: China
Study
Depressed Teens More
Likely to Smoke
363
Suicide Higher in Areas with Guns
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
Pollution Linked with Birth Defects in US Study
Snacks Key to Kids’ TV- Linked Obesity: China
Study
Depressed Teens More
Likely to Smoke
Ties, Links, Relationships, and Associations
364
1. Cause
2. Confounding
3. Reverse Time Order
4. Chance
5. Bias
Possible Explanations for Finding an Association
365
Epidemiology
Epidemiology
... the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems.
Leon Gordis, Epidemiology, 3rd Edition, Elsevier Saunders, 2004.
366
1. Cause
2. Confounding
3. Reverse Time Order
4. Chance
5. Bias
Possible Explanations for Finding an Association
367
Cause
A factor that produces a change in another factor.
William A. Oleckno, Essential Epidemiology: Principles and Applications, Waveland Press, 2002.
Possible Explanations for Finding an Association
368
Sample of 100
369
Sample of 100, 25 are Sick
370
Diagram
2x2 Table
DZ DZ
X
X
a bc d
Types of Causal Relationships
371
DZ DZ
X
X
a bc d
Diagram
2x2 Table
Types of Causal Relationships
372
Handout
373
374
X1
X1
X1
X1
X1
X1
X1
X1
X1 X1
X1
X1X1X1
X1X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1 DZ
DZ DZ
X1
X1
a bc d
Diagram
2X12 Table
Necessary and Sufficient
X1
375
DZ DZ
a bc d
X1 DZX2 X3+ +X1
X1
X1
X1
X1
X1
X1
X1
X1 X1
X1
X1X1X1
X1X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1X1
Diagram
2X12 Table
Necessary but Not Sufficient
X1
X1
376
X1
X1
X1
X1
X1
X1
X1
X1 X1
X1
X1X1
X1
X1
X1
X1
DZ DZ
a bc d
X2 DZ
X1
X3
Diagram
2X12 Table
Not Necessary but Sufficient
X1
X1
377
DZ DZ
a bc d
X1
X1
X1
X1
X1
X1
X1 X1
X1X1X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1
X1X1
X4
X1
X7
DZX5 X6+ +
X2 X3+ +
X8 X9+ +
Not Necessary and Not Sufficient
Diagram
2X12 Table
X1
378
X
X
X
X
X
X
X
X
X X
X
XXX
XX
X
X
X
X
X
X
X
X
X
X DZ
DZ DZ
X
X
a bc d
X
Diagram
2x2 Table
Necessary and Sufficient
379
DZ DZ
X
X
a bc d
X DZX X+ +
X
X
X
X
X
X
X
X
X
X X
X
XXX
XX
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
XX
Diagram
2x2 Table
Necessary but Not Sufficient
380
X
X
X
X
X
X
X
X X
X
XX
X
X
X
X
DZ DZ
X
X
a bc d
X
X DZ
X
X
Diagram
2x2 Table
Not Necessary but Sufficient
381
DZ DZ
X
X
a bc d
X
X
X
X
X
X
X
X X
XXX
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
XX
X
X
X
DZX X+ +
X X+ +
X X+ +
Not Necessary and Not Sufficient
Diagram
2x2 Table
382
a b
c d
Heart Attack
NoHeart Attack
Lack of Fitness
No Lack of Fitness
Lack of fitness and physical activity causes heart attacks.
383
a b
c d
Lead Poisoning
NoLead
Poisoning
Lack of Supervision
No Lack of
Supervision
Lack of supervision of small children causes lead poisoning.
384
385
Is the association causal?
386
Suicide Higher in Areas with Guns
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
Pollution Linked with Birth Defects in US Study
Ties, Links, Relationships, and Associations
1. Cause
2. Confounding
3. Reverse Time Order
4. Chance
5. Bias
Snacks Key to Kids’ TV- Linked Obesity: China
Study
Depressed Teens More
Likely to Smoke
387Teach Epidemiology
Enduring Epidemiological Understandings
388
389
1. Cause
2. Confounding
3. Reverse Time Order
4. Chance
5. Bias
Possible Explanations for Finding an Association
390
All the people in a particular group.
Population
Possible Explanations for Finding an Association
391
A selection of people from a population.
Sample
Possible Explanations for Finding an Association
392
Inference
Process of predicting from what is observed in a sample to what is not observed in a population.
To generalize back to the source population.
Possible Explanations for Finding an Association
393
Sample
Population
Process of predicting from what is observed
to what is not observed.
Observed
Not Observed
Inference
394
Deck of
100 cards
Population
395
a
25 cards
b
25 cards
c
25 cards
25 cards
d
Population
396
=
Population
a
25 cards
b c d
25 cards25 cards25 cards
=a b
c d
Odd #
Even #
No Marijuana
No Marijuana
Population
Total
397
=
Population
a
25 cards
b c d
25 cards25 cards25 cards
= 2525
25 25
50
50
Total
Odd #
Even #
No Marijuana
No Marijuana
Population
398
=
Population
=M&M’s
No M&M’s
FluNo
Flu
2525
25 25
50
50
Total
=
2525
25 25
50
50
Total
a
25 cards
b c d
25 cards25 cards25 cards
Odd #
Even #
No Marijuana
No Marijuana
Population
399
=
Population
=
2525
25 25
50
50
Total
a
25 cards
b c d
25 cards25 cards25 cards
Risk
25 / 50 or 50%
25 / 50 or 50%
Odd #
Even #
No Marijuana
No Marijuana
Population
400
=
Population
a
25 cards
b c d
25 cards25 cards25 cards
=
2525
25 25
50
50
Total Risk Relative Risk
25 / 50 or 50 %
25 / 50 or 50 %50 % / 50% = = 1
50 %
50 %
____Odd #
Even #
No Marijuana
No Marijuana
Population
401
25 cards
25 cards
25 cards
25 cards
Population
402
To occur accidentally.
To occur without design.
Chance
A coincidence.
Possible Explanations for Finding an Association
403
Chance
404
Chance
405
Population
Sample
b
Sample
of
20 cards25 cards25 cards25 cards25 cards
Sample
406
Population
Sample
b
Sample
of
20 cards25 cards25 cards25 cards25 cards
10
10
Total
55
5 5Odd #
Even #
No Marijuana
No Marijuana
Sample
407
Population
Sample
b
Sample
of
20 cards25 cards25 cards25 cards25 cards
10
10
Total
55
5 5
Risk
5 / 10 or 50 %
5 / 10 or 50 %Odd #
Even #
No Marijuana
No Marijuana
Sample
408
Population
Sample
b
Sample
of
20 cards25 cards25 cards25 cards25 cards
10
10
Total
55
5 5
Risk
5 / 10 or 50 %
5 / 10 or 50 %Odd #
Even #
No Marijuana
No Marijuana
Sample
Relative Risk
50 % / 50% = = 150 %
50 %
____
409
b
Sample
of
20 cards
TotalRisk
5 / 10 = 50 %
5 / 10 = 50 %
50 1
Relative Risk
By Chance CDC
% ___
%
=Odd #
Even #
No Marijuana
No Marijuana
Sample
410
10
10
Total
55
5 5
Risk
5 / 10 or 50 %
5 / 10 or 50 %
Relative Risk
How many students picked a sample with 5 people in each cell?
= 150 %
50 %
____
Odd #
Even #
No Marijuana
No Marijuana
Chance
By Chance
411
Relative Risks
Greater than 1 Less than 1
Chance
412
Study Links Having an Odd Address to Marijuana Use
Ties, Links, Relationships, and Associations
413
Relative Risks
Greater than 1 Less than 1
Possible Explanations for Finding an Association
414
Study Links Having an Even Address to Marijuana Use
Ties, Links, Relationships, and Associations
415
Relative Risks
Greater than 1 Less than 1
1
By ChanceBy Chance
25 cards25 cards25 cards25 cards
Chance
416
b
Sample
of
20 cards
TotalRisk
5 / 10 = 50 %
5 / 10 = 50 %
50
Relative Risk
50
%___
%
=Odd #
Even #
No Marijuana
No Marijuana
Different Sample Sizes
417
Relative Risks
Greater than 1 Less than 1
1
By ChanceBy Chance
25 cards25 cards25 cards25 cards
Chance
50 cards
418
b
Sample
of
20 cards
TotalRisk
5 / 10 = 50 %
5 / 10 = 50 %
50
Relative Risk
75
%___
%
=Odd #
Even #
No Marijuana
No Marijuana
Different Sample Sizes
419
Relative Risks
Greater than 1 Less than 1
1
By ChanceBy Chance
25 cards25 cards25 cards25 cards
Chance
75 cards
420
b
Sample
of
20 cards
TotalRisk
5 / 10 = 50 %
5 / 10 = 50 %
50 1
Relative Risk
99
%___
%
=Odd #
Even #
No Marijuana
No Marijuana
Different Sample Sizes
421
Relative Risks
Greater than 1 Less than 1
1
By ChanceBy Chance
25 cards25 cards25 cards25 cards
Chance
99 cards
422
Suicide Higher in Areas with Guns
Family Meals Are Good for Mental Health
Lack of High School Diploma Tied to US Death
Rate
Study Links
Spanking to
Aggression
Study Concludes: Movies Influence
Youth Smoking
Study Links Iron
Deficiency to Math
Scores
Kids Who Watch R-Rated Movies More Likely to Drink, Smoke
1. Cause
2. Confounding
3. Reverse Time Order
4. Chance
5. Bias
Snacks Key to Kids’ TV- Linked Obesity: China
Study
Depressed Teens More
Likely to Smoke
Association is not necessarily causation.
Ties, Links, Relationships, and Associations
423Teach Epidemiology
Enduring Epidemiological Understandings
424
425
Revised
Teach Epidemiology
Teach Epidemiology
426
Time Check
3:30 PM
427
428Teach Epidemiology
Enduring Epidemiological Understandings
Teach Epidemiology
Explaining Associations and Judging Causation
1. Cause
2. Confounding
3. Reverse Time Order
4. Chance
5. Bias
Teach Epidemiology
Explaining Associations and Judging Causation
Coffee and Cancer of the Pancreas
431
432
Guilt or Innocence?Causal or Not Causal?
Does evidence from an aggregate of studies support a cause-effect relationship?
Teach Epidemiology
Explaining Associations and Judging Causation
433
Sir Austin Bradford Hill “The Environment and Disease:
Association or Causation?” Proceedings of the Royal Society of Medicine
January 14, 1965
Teach Epidemiology
Explaining Associations and Judging Causation
Handout
434
“In what circumstances can we pass from this observed association
to a verdict of causation?”
Teach Epidemiology
Explaining Associations and Judging Causation
435
“Here then are nine different viewpoints from all of which we should study association
before we cry causation.”
Teach Epidemiology
Explaining Associations and Judging Causation
Does evidence from an aggregate of studies support a cause-effect relationship?
1. What is the strength of the association between the risk factor and the disease?
2. Can a biological gradient be demonstrated?
3. Is the finding consistent? Has it been replicated by others in other places?
4. Have studies established that the risk factor precedes the disease?
5. Is the risk factor associated with one disease or many different diseases?
6. Is the new finding coherent with earlier knowledge about the risk factor and the m disease?
7. Are the implications of the observed findings biologically sensible?
8. Is there experimental evidence, in humans or animals, in which the disease has m been produced by controlled administration of the risk factor?
Teach Epidemiology
Explaining Associations and Judging Causation
Handout
Teach Epidemiology
Explaining Associations and Judging Causation
Timeline
Cohort Study
Randomized Controlled Trial
Timeline
Case-Control Study
Timeline
Cross-Sectional Study
Timeline
E
E
O
O
O
O
E
E
E
E
Healthy PeopleHealthy People
E
Random Assignment
E
O
O
O
O
Healthy PeopleHealthy People
E
E
O
O
O
O
Teach Epidemiology
Explaining Associations and Judging Causation
Teach Epidemiology
Explaining Associations and Judging Causation
Handout
440
Stress causes ulcers.
Helicobacter pylori causes ulcers.
Teach Epidemiology
Explaining Associations and Judging Causation
441
*
*
*
**
*
*
*
*
Teach Epidemiology
Explaining Associations and Judging Causation
442Teach Epidemiology
Explaining Associations and Judging Causation
443
Time Check
4:30 PM
444