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Laying out the data
Designing effective tables
FETP India
Competency to be gained from this lecture
Lay out data effectively in tables
Key areas
• Essential rules when arranging a table• Common tables in epidemiology
Communicating patterns and messages contained in your data
• Show the patterns inherent in the data• Focus attention on these patterns• Serve as a basis for narrative or
discussion• Lead observer to insight, discussion,
conclusions
Avoid visual puzzles in tables
• Poorly organized data• Series of complicated numbers• Important data obscured• Unnecessary frames, lines, coloring• Decoration
Basic table rules
Column headings
Data
Footnotes
Title
Row headings
Typical table layout with components
Making sure that a table is understandable without referral
to other material • Title
Person Time Place Any measurement found in all columns
• Row and column headings Content of the row or column Any modifier applied to all cells of a row or column Unit of measurement Abbreviations, if necessary
Basic table rules
Using footnotes in a table
• Clarify points of potential ambiguity• Explain all:
Abbreviations Symbols Codes
• Note exclusions • Mention data source if applicable
Basic table rules
*ASC Ehrenberg, J R Statis Soc A, 140(3):277-297, 1977
Suggestions for data arrangement in tables *
1. Round data to 2 meaningful figures2. Summarize rows and columns3. Compare numbers in columns 4. Arrange key data by magnitude5. Help the reader with easy table layout6. Align numbers by decimal
Basic table rules
Table with excessive number of meaningful figures
Factor Cases RateRate Ratio pa
None 27451 2.345 1.000 Refb
A 34211 3.433 1.464 0.1011
B 11002 5.661 2.414 0.0133
C 5643 6.001 2.559 0.0005
a. p-valueb. Reference exposure category
Up to five meaningful figures
Rate ratios difficult to compare
1. Round data to 2 meaningful figures
Basic table rules
Rounding data in a table to 2 meaningful figures
Factor
Cases(1000s
) RateRate ratio p
None 27 2.3 1.0 Ref*
C 34 3.4 1.5 >0.100
A 11 5.7 2.4 <0.050
B 06 6.0 2.6 <0.001
a. p-valueb. Reference exposure category
2 meaningful figures
Rate ratios easier to compare
1. Round data to 2 meaningful figures
Basic table rules
Year M FBoth Sexes
1973 500 99 600
1970 580 87 670
1968 460 89 550
1966 260 71 330
Mean 430 86 520
Summary of the columns
Summary of the rows
2. Summarize rows and columns
Summarizing rows and columns with totals, averages or other statistics
Basic table rules
Compare numbers in columns
23 42 34 109 87 42 27 98 114 75
Difficult to compare numbers in rows
23 42 34
109 87 42 27 98
114 75
1st improvement: Right-justify numbers
vertically 2327
34424275
87 98109
114
2nd improvement: Sort numbers
3. Compare numbers in columns
Basic table rules
Organize data by magnitude
Exposure
Cases(1000
s) RateRate ratio Pa
A 11 2.9 1.3 > 0.100
B 06 9.9 4.3 < 0.001
C 34 5.4 2.3 > 0.100
None 27 2.3 1.0 Refb
4. Arrange key data by magnitude
a. p-value
b. Reference exposure category Basic table rules
Organize data by magnitude
Exposure
Cases(1000s
) RateRate ratio pa
B 6 9.9 4.3 < 0.010
C 34 5.4 2.3 < 0.050
A 11 2.9 1.3 > 0.001
None 27 2.3 1.0 Refb
a. p-value
b. Reference exposure category
4. Arrange key data by magnitude
Basic table rules
YearBothsexes Male Female
1973 600 500 99
1970 670 580 87
1968 550 460 89
1966 330 260 71
Spaced out table layout: Comparisons difficult for the reader
5. Help the reader with easy table layout
Basic table rules
YearBothsexes Male Female
1973 600 500 99
1970 670 580 87
1968 550 460 89
1966 330 260 71
5. Help the reader with easy table layout
Drawing columns and rows close together facilitates comparisons
Basic table rules
Intervening statistics: Separated numbers are harder to compare
Rate per 1000
Year Male Female All
1993 83 78 80
2.3 2.2 1.9
1994 62 66 63
2.5 2.7 1.8
1995 58 54 56
2.1 2.0 1.7
1996 55 45 51
2.0 2.0 1.7
5. Help the reader with easy table layout
Basic table rules
Rate per 1000 (SE)
Year Male Female All
1993 83 (2.3) 78 (2.2) 80 (1.9)
1994 62 (2.5) 66 (2.7) 63 (1.8)
1995 58 (2.1) 54 (2.0) 56 (1.7)
1996 55 (2.0) 45 (2.0) 51 (1.7)
Moving and minimizing intervening numbers facilitates readability
5. Help the reader with easy table layout
Basic table rules
Rate per 1000a
Year M F All
1993 83 78 80
1994 62 66 63
1995 58 54 56
1996 55 45 51
a. Standard errors for all rates less than 5% of rate.
Remove intervening numbers entirely if consequence minimal
5. Help the reader with easy table layout
Basic table rules
Align columns by decimal
23 42 34
10.9 8.7 42 27 9.8 114 75
23.0 42.0 34.010.9 8.7
42.0 27.0
9.8 114.0
75.0
Keeping the zeros or not is a question of personal style
6. Align numbers by decimal
Basic table rules
Arranging common types of tables in epidemiology
• Text table• Line listing• Two variable table• Complex table• Cohort study• Case-control study
Common tables
Text table
Between July 1 and August 31, 72 cases occurred in three classes of school A.
Class Cases 1 23 2 31 3 18 No cases occurred in the six other classes.
a. Text table
Common tables
State Age1 Sex Days2 Dose
New York 02 M 03 1
California 03 M 03 1
Pennsylvania 06 M 03 1
Pennsylvania 02 M 04 1
Colorado 04 F 04 1
California 07 M 04 2
Kansas 02 F 05 1
Colorado 03 M 05 1
New York 03 F 05 1
North Carolina 04 F 05 1
Missouri 11 M 05 1
Pennsylvania 03 F 07 1
California 04 F 14 2
Pennsylvania 02 M 29 1
California 05 M 59 1
1. Age in months
* MMWR, 48 (27):577
2. Days from dose to symptom onset
Reported cases of intussusception among recipients of rotavirus
vaccine, by state, United States, 1998-1999*
b. Line listing
Common tables
New cases of primary and secondary syphilis by age group and sex, United States, 1989
Age group Cases (100’s)
(years) Male Female Total
14 0.4 1.9 2.3
15-19 17.4 27.9 44.3
20-24 51.4 53.9 100.3
25-29 53.4 42.9 96.3
30-34 55.4 31.9 86.3
35-44 50.4 19.9 69.3
45-54 21.4 49.9 26.3
55 11.4 13.9 13.3
Total 260.4 180.9 440.3
c. Two variable table
Common tables
Complex table
Children
Character Exp %(n=205)
Not exp%(n=8729) p
Gestational age (weeks) at birth
<25 5.8 14 0.04
25-29 18.0 19 NS
Birthweight (kg)
1.5 -- 15 .0 15 NS
2.5 -- 39 .0 43 NS
d. Complex table
Common tables
Exposed
% Yes No
Exposure Res. a % ARb ARb RRc (95% CId)
Type 1
Sub Type 1-A ( - )
Sub Type 1-B ( - )
Sub Type 1-C ( - )
Type 2 ( - )
Type 3 ( - )
Type 4:
a. Res. = Responded
c. RR = Risk Ratio
b. AR = Attack Rate – cases per ___
d. 95% CI = 95% confidence interval of the RR
e. Cohort study
Risk of ______ by exposure, among #### residents of Place, time
Common tables
Exposed
Exposure % AR a RR b 95% CI c
Type or Level 3
Type or Level 2
Type or Level 1
None or Level 0 1.0 Referent
b. RR = Risk Ratio
c. 95% CI = 95% confidence interval of the RR
a. AR = Attack Rate – cases per ___
Risk of ______ by exposure, among #### residents of Place, time
e. Cohort study (reference group)
Common tables
Exposed % (n) a
Exposure Cases Controls OR b 95% CI c
Type 1 (n) (n) ( – )
Sub Type 1-A (n) (n) ( – )
Sub Type 1-B (n) (n) ( – )
Sub Type 1-C (n) (n) ( – )
Type 2 (n) (n) ( – )
Type 3 (n) (n) ( – )
c. 95% CI = 95% confidence interval of the OR
a. n = subjects responding b. OR = Odds Ratio
Exposures (%) among ### cases and ### controls, Place, Time
f. Case control study
Common tables
Take home messages
• Design your table around the message that is contained in your data
• Refer to templates that apply to the table you are trying to design