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4/12/2013
1
Workshop Topic Presenters Date
Research Ethics & Governance Dr Tam Nguyen 14-Feb-13
Introduction to Clinical Research Dr Harin Karunajeewa 28-Feb-13
Evaluating the literature A/Professor Kerrie Sanders 14-Mar-13
Writing a research proposal Dr Lizzie Skinner 28-Mar-13
Beginners statistics: Study Design Professor Danny Liew 11-Apr-13
Referencing and EndNote Dr Tam Nguyen & Lynn Higgins 24-Apr-13
Mixed Methods: Quantitative & Qualitative Professor Terrence McCann 9-May-13
Using Excel for research Dr Lizzie Skinner 23-May-13
Making sense of your results Professor Danny Liew 6-Jun-13
Getting your work published A/Professor Kerrie Sanders 20-Jun-13
Writing Abstract for Research Week/ Conferences Dr Debra Kerr 4-Jul-13
WH RESEARCH TRAINING WORKSHOP 2013
Date: Thursdays ,12:30-1:30pm
Venue: Auditorium Western Centre for Health Research & Education Sunshine Hospital
Introduction to Study
Designs and Biostatistics
Danny Liew
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Overview
• overview of study designs
• observational studies
• clinical trials
• basic biostatistics
Classification of Study Designs
observational
• [case series, case reports]
• ecological
• cross-sectional
• case-control
• cohort
interventional
• clinical trials
descriptive
analytical
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Classification of Study Designs
observational
• [case series, case reports]
• ecological
• cross-sectional
• case-control
• cohort
interventional
• clinical trials
non-longitudinal
longitudinal
Ecological Studies
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• study of data at population/group level -
no data on individuals
• easily and opportunistically undertaken,
often using routinely collected data
• hypothesis-generating studies
Ecological Studies
SMOKING
14012010080604020
CA
NC
ER
140
120
100
80
60
40
20
Dis
ease
inci
dence
Average smoking (cig/week)
plots of individual countries
Ecological Study - Hypothetical Example
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Cross-Sectional Studies
• sample of population selected and information
obtained at one point/period in time
• large studies can take place over years, but each
subject contributes data only once
• that is, there is no follow-up of subjects
Cross-Sectional Studies
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• data collected via:
questionnaires ± examinations ± investigations
• mostly descriptive outputs, especially prevalence
eg, of CHD among Australians
Cross-Sectional Studies
Example of Cross-Sectional Study
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Case Control Studies
Case Control Studies
• comparison of previous exposure status between:
–subjects with outcome of interest (cases)
–subjects without outcome of interest (controls)
• controls are often matched with cases, 1:1 or n:1
• matching by confounders - eg: age, sex
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exposure outcome
time
Case Control Studies
step 1: define and recruit cases; recruit controls by matching to cases (outcome ascertainment 1st)
step 2: determine previous exposure among subjects
Case Control Studies
• explicit knowledge about temporal relationship
between exposure and outcome
• useful for studying rare outcomes
• key output: odds ratio, approximation of relative risk
of outcome conferred by exposure
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200
150
100
150
Controls: no Kafoop’s Syndrome
OR = (200*150) / (100*150)
= 2.0
Interpretation: smoking doubles likelihood of Kafoop’s Syndrome
Hypothetical Example
Cases: Kafoop’s Syndrome
No smoking
Smoking
Kafoop’s Syndrome
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Cohort Studies
Cohort Studies
• longitudinal, with follow-up of subjects
• collect incidence data
• comparison of outcomes between/among subgroups
eg, not exposed vs exposed to risk factor
• derive relative risks
(recall examples from British Doctor’s Study)
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exposure outcome
time
Prospective Cohort Study
Key: explicit knowledge about the temporal relationship between exposure and outcome.
exposure outcome
time
Retrospective Cohort Study
Key: explicit knowledge about the temporal relationship between exposure and outcome.
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• explicit (often-detailed) knowledge about temporal
relationship between exposure and outcome
• can include multiple exposures and outcomes
• research hypotheses can be addressed post hoc in
established cohorts
Cohort Studies
The Framingham Heart Study
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Framingham Risk Equation
Clinical Trials
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“Clinically Proven”
“Is it all a male conspiracy?” The Age 11 July 2002
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Clinical Trials
• longitudinal studies designed to assess if an
intervention (removal of exposure) changes
the incidence of an outcome
• most interventions are expected to decrease
the incidence of the outcome
• most involve a control group for comparison
prospective follow-up to capture outcomes
assign intervention
intervention A
placebo / intervention B
Clinical Trials
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• ‘gold standard’ for evidence of causality
–active change of exposure status
–tightly controlled study environment
• provides most of the evidence for EBP
Clinical Trials
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Key Outcomes
relative measures of intervention effect:
• relative risks
• hazard ratios
absolute measures of intervention effect:
• absolute risk/rate reduction
• number needed to treat
survival analysis
Randomisation
• random allocation of subjects into each
arm of a clinical trial
• objective: treatment groups identical in
all aspects other than the intervention
• rationale: reduce confounding
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Confounding
exposure
confounder
outcome
Confounding in Clinical Trials
intervention
confounder (age/sex etc...)
outcome
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JAMA 2002; 288: 321-333.
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Basic Biostatistics
Studies and Samples
• studies are undertaken on samples of the population
of interest (cf census)
• studies are used to make inferences about the
population of interest
• biostatistics is concerned with the extent to which
study (sample) results reflect the ‘truth’
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p value
• probability of the study result if it is assumed that the
null hypothesis applies - truly no difference between the
groups being compared
• ie, probability that the study result was a chance finding
• p value = conventional cut-off = 0.05
p < 0.05: statistically significant
p ≥ 0.05: not statistically significant
JAMA 2002; 288: 321-333.
p = 0.02 p = 0.01
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95% Confidence Interval
• interval within which there is 95% confidence that the
‘true’ value lies
• if the null value is excluded, result is stat significant
• null value: value if the null hypothesis applies
• null value: 1.0 for ratios (eg HR, RR, OR) and 0 for
differences (eg absolute risk differences)
JAMA 2002; 288: 321-333.
4/12/2013
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WH RESEARCH TRAINING WORKSHOP 2013
Date: Thursdays ,12:30-1:30pm
Venue: Auditorium Western Centre for Health Research & Education Sunshine Hospital
Workshop Topic Presenters Date
Research Ethics & Governance Dr Tam Nguyen 14-Feb-13
Introduction to Clinical Research Dr Harin Karunajeewa 28-Feb-13
Evaluating the literature A/Professor Kerrie Sanders 14-Mar-13
Writing a research proposal Dr Lizzie Skinner 28-Mar-13
Beginners statistics: Study Design Professor Danny Liew 11-Apr-13
Referencing and EndNote Dr Tam Nguyen & Lynn Higgins 24-Apr-13
Mixed Methods: Quantitative & Qualitative Professor Terrence McCann 9-May-13
Using Excel for research Dr Lizzie Skinner 23-May-13
Making sense of your results Professor Danny Liew 6-Jun-13
Getting your work published A/Professor Kerrie Sanders 20-Jun-13
Writing Abstract for Research Week/ Conferences Dr Debra Kerr 4-Jul-13
