Tables, graphs, and diagrams Barbara Schimmer Jurmala, Latvia, 2006 Based on EPIET material.
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Transcript of Tables, graphs, and diagrams Barbara Schimmer Jurmala, Latvia, 2006 Based on EPIET material.
Tables, graphs, and diagrams
Barbara SchimmerJurmala, Latvia, 2006
EpidemiologyTra ining
Based on EPIET material
Contents
• Use of tables, graphs and graphics
• Graphics in descriptive epidemiology° describe
• Graphics in analytical epidemiology° compare
• Designing graphics
Background
Epidemiology
Purpose• Description
° Time° Place° Person
• Clinical features
• Comparison° Odds ratios° Relative risks
Methods• Surveillance• Outbreak
investigations• Other studies:
clinical epidemiologyfield trialsexperimental epidemiology
Use of data tables and graphics?
Process data
• Organisetriage,
cleaning
• Summariseaggregate
• Explore° trends° relationships° errors
Present data
• Communicate
• Paper• Poster• Screen
static animated
Paper vs. screen
Paper
• Time unlimited• Repetition• Details
notes?• White, grey and
black
Screen
• Time < 1 min• No repetition• Less details• Colours possible
Tables, graphics, and diagrams
• Self-explanatory
• Simple!
• Title
(what, who, where, when)
• Define abbreviations and symbols
• Note data exclusions
• Reference the source
Time
The epidemic curve 1
Figure 1. Reported cases of campylobacteriosis (n=45) in Svolvær, Norway, by
date of onset J anuary and February 1997.
10 = 1 primary case
= 1 secondary household case
5
22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10
J anuary February
The epidemic curve 2
• Histogram° Area proportional to number
° No space between columns
° One population
• X-axis = time° Start before epidemic, continue after
° Interval ≤1/4 of incubation period
• Y-axis = number of cases° Usually one square = one case
Easy to make in Excel
The arithmetic-scale line graph 1
Figure 2. Incidence rate of gonorrhoea and syphilis in Norway, 1975-1999
0
100
200
300
400
1975 1978 1981 1984 1987 1990 1993 1996 1999Year
Gonorrhoea
Syphilis
Cases per 100,000
Source: Folkehelsa
The arithmetic-scale line graph 2
• For time series
• Show actual changes in magnitude
• X-axis = time
• Y-axis = rate (or number) of cases° Start at 0
° Breaks possible, clearly marked
The semilogarithmic-scale line graph 1
Figure 3. Incidence rate of gonorrhoea and syphilis in Norway, 1975-1999
0,1
10
1000
1975 1978 1981 1984 1987 1990 1993 1996 1999Year
Gonorrhoea
Syphilis
Cases per 100,000
The semilogaritmic-scale line graph 2• For time series when
° interested in rate of change
• X-axis = time arithmetic
• Y-axis = rate (or number) of cases, logarithmic° Straight slope = constant rate of change
° Steep slope = constant rapid change
° Parallell lines = same rate of change
° Change in slope = acceleration deceleration of rate
° Start at lowest cycle, e.g. 0.1-1 or 1-10
° No breaks
In graphs...
• Labels for axes, scales and legends
• Legends or keys if >1 variable
• Scale divison, appropriate scale
• Units of measurements in title
• No grid, no numbers
• No 3D
Place
The one-variabletable
Table 4. Cases of meningococcal
disease in Dublin 1998 by area of
residence
Area
n %
1 2 5
2 1 3
3 2 5
4 2 5
5 8 22
6 7 19
7 10 27
8 2 5
9 2 5
10 1 3
Total 37 100
Cases
The spot map
8
67
12
34
5
910
Figure 1. Cases of meningococcal disease in Dublin 1998 by place of residence.
1 dot = 1 case
The area dot (or dot density) map
8
67
12
34
5
910
Figure 2. Cases of meningococcal disease in Dublin 1998 by area of residence.
1 dot = 1 case
The area map
8
67
12
34
5
910
Figure 3. Incidence rate (per 100,000) of meningococcal disease in Dublin 1998 by area of residence.
Person
The two-variable table
Table 1. Cases of Salmonella
Typhimurium-infection by age-group and sex,
Herøy, Norway, 1999
Age group Total
(years) Male Female
0 - 9 7 5 12
10 - 19 5 5 10
20 - 29 5 5 10
30 - 39 1 4 5
40 - 49 2 3 5
50 - 59 0 3 3
60 - 69 2 1 3
70 - 2 4 6
Total 24 30 54
Sex
Grouped bar chart
Figure 1. Cases of S Typhimurium-infection by age-group and sex, Herøy, Norway, 1999
0
2
4
6
8
0 - 9 10 - 19 20 - 29 30 - 39 40 - 49 50 - 59 60 - 69 70 -
Age-group
Male
Female
Number of cases
Stacked bar chartFigure 1. Cases of S Typhimurium-infection by age-group and sex, Herøy, Norway, 1999
0 2 4 6 8 10 12 14
0 - 9
10 - 19
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
70 -
Age-group
Number of cases
Male
Female
Component bar chartFigure 1. Cases of S Typhimurium-infection by age-group and sex, Herøy, Norway, 1999
0 %
20 %
40 %
60 %
80 %
100 %
0 - 9 10 - 19 20 - 29 30 - 39 40 - 49 50 - 59 60 - 69 70 -
Age-group
Male FemaleProportional distribution by sex
Bar charts
• Order° Natural
° Decreasing or increasing
• Vertical or horizontal
• Same width of bars
• Length = frequency
• Space between bars and groups, but not within groups
• Tables are often better
Pie chart
Figure 4. Cases of S Typhimurium-infection by age-group, Herøy, Norway, 1999.
21 %
19 %
19 %
9 %
9 %
6 %
6 %
11 % 0 - 9
10 - 19
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
70 -
Clinical features
TableTable 5. Clinical symptoms among 54 patients with S
Typhimurium-infection, Oslo, Norway, May 1998
Symptoms
n %
Diarrhoea 54 100
Fever 35 65
Headache 12 22
J oint pain 4 7
Muscle pain 4 7
Cases
Birth weight of 36217 newbornsDistribution of newborns by birth weight (2500-4500g)
0
200
400
600
800
1000
1200
2500
2550
2610
2660
2705
2750
2790
2824
2870
2920
2950
2990
3010
3042
3070
3102
3149
3190
3230
3265
3305
3350
3380
3410
3440
3460
3520
3560
3615
3655
3690
3740
3765
3810
3850
3900
3940
3980
4025
4055
4090
4150
4210
4237
4280
4340
4390
4440
4500
weight
co
un
t
Anything wrong with the distribution ?Distribution of newborns by birth weight (3300-3500g)
0
200
400
600
800
1000
1200
3300
3305
3310
3320
3330
3340
3345
3350
3355
3357
3360
3365
3370
3380
3385
3390
3395
3400
3401
3410
3415
3420
3430
3431
3434
3440
3441
3445
3449
3450
3455
3460
3470
3480
3490
3500
weight (g)
ca
se
s
Anything else than the relation ?Relation of birth weight and birth length
0
10
20
30
40
50
60
70
0 1000 2000 3000 4000 5000 6000
weight (g)
len
gth
(cm
)
Comparison
The 2x2 table for a cohort study
Table 5. Association between fish consumption and
gastrointestinal illness among customers at Uncle Mike's Fish &
Chips, Cambridge, October 1 2000
Ill Well Total Attack rate
Ate fish 42 16 58 0.72
Did not eat fish 5 59 64 0.078
Relative risk: 9.3 (95% confidence interval 3.9 - 22)
The 2x2 table for a case control study
Table 6. Association between fish consumption and
gastrointestinal illness among customers at Uncle Mike's Fish &
Chips, Cambridge, October 1 2000
Cases Controls Total
Ate fish 34 20 54
Did not eat fish 8 62 70
Total 42 82 124
Odds ratio: 13 (95% confidence interval 5.3 - 33)
Table from a case control study
Table 5. Association between exposures and campylobacteriosis in case-control
study, Oslo, Norway, 1998. Univariate, matched analysis.
Exposure Cases Controls Odds 95% conf.
ratio interval
Eaten at pizza restaurant 9/37 12/70 1.8 0.62 - 5.0
Eaten at party 10/36 9/74 3.2 0.97 - 11
Eaten foods from deli 23/37 42/74 1.2 0.56 - 2.7
Eaten unpeeled fruits 19/37 54/74 0.27 0.10 - 0.78
Close contact with a case 7/35 2/72 13 1.5 - 110
Drank >4 glas of water per day 21/37 33/74 1.7 0.73 - 3.9
Customer of water company B 27/37 33/74 4.0 1.3 - 7.3
Design
Think data-ink
Every bit of ink should have a reason
Designing graphics
• Show the data
• Use ink for the data
• Remove unnecessary ink
• Remove gimmicks
• No 3D
• Careful with colours
Standard symbols in tablesAvereage BMI by category of weight
weight men women
40-49 - .
50-59 19,8 21,8
60-69 23,1 24,8
70-79 25,0 27,6
80-89 27,4 30,5
90-99 29,8 34,2
explanation of symbols- = we measured, no case in this category, we can´t say that it is 0. = we measured, but we cant calculate the average of 1 case
Standard symbols in tables
Cause specific mortality
Cause of death men women
CVD 50 35
Pneumonia 45 30
CA prostatae 10 x
CA cervicis uteri x 10
explanation of symbolsx = not displayed for logical reasons
0102030405060708090
No.
of
case
s
B C Y W Unknown
Serogroup
Cases of meningococcal disease in Dublin by serogroup
Cases of meningococcal disease in Dublin by serogroup
0
10
20
30
40
50
60
70
80
90
B C Y W Unknown
Serogroup
No.
of
case
s
Cases of meningococcal disease in Dublin by serogroup
0
10
20
30
40
50
60
70
80
90
B C Y W Unknown
Serogroup
No.
of
case
s
Cases of meningococcal disease in Dublin by serogroup
0
20
40
60
80
B C Y W Unknown
Serogroup
No.
of
case
s
Summary
• Use of graphics Explore and present• Presentation Paper vs screen• Description
° Time - line graphs or epicurves° Place - maps or tables° Person - tables or bar charts° Clinical - tables
• Analysis° Comparison - 2x2 tables, other tables
• Design Save your ink!