Data presentation
Tables, graphs and maps
Integrated Disease Surveillance Programme (IDSP)
district surveillance officers (DSO) course
Outline of the session
1.
2.
3.
4.
Analogical versus digital information
Tables
Graphs
Maps
2
Communicating quantitative information
• Analogical communication: Graphs
 Less precise
 More graphic
 Provides overall understanding
• Digital communication: Tables
 Precise
 Numeric
 Provides detailed and exact description
7:00 am
3
Digital and analogical information
Number of cases
Cases of monkeypox by month of onset,
Katako-Kombe, Zaire, 1996-1997
30
Example: Analogical display
of information (Graph)
25
Secondary cases
20
Primary cases
15
10
5
0
Feb Mar Apr May Jun
1996
Jul
Aug Sep
Oct Nov Dec Jan Feb
1997
Month of onset
WHO-CDC
4
Digital and analogical information
Cases of Monkeypox by month of onset,
Katako-Kombe, Zaire, 1996-1997
Feb-96
Mar-96
Apr-96
May-96
Jun-96
Jul-96
Aug-96
Sep-96
Oct-96
Nov-96
Dec-96
Jan-97
Feb-97
Total
Primary cases
2
0
2
5
0
4
3
1
1
3
0
2
1
24
Example: Digital display
of information (Table)
5
Secondary cases
0
3
2
6
5
9
23
5
2
1
0
0
9
65
Digital and analogical information
Tables
• Presentation of detailed analyzed data
• Do not present raw data
 E.g., lists
• Present analyzed data with summary
statistics
6
Tables
Typical table layout with components
Title
Column headings
Data
Row headings
Footnotes
7
How to make sure that the cells of the
table are understandable without
referral to other material
• Title
 Time, Place and Person information
 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)
• Footnotes




Clarify potential ambiguities
Explain abbreviations, symbols, codes
Note exclusions
Mention data source
8
Tables
Selected suggestions for data
arrangement in tables
1.
2.
3.
4.
Summarize rows and columns
Compare numbers in columns
Arrange key data by magnitude
Align numbers by decimal
9
Tables
1. Summarize rows and columns
Summarize rows and columns with
totals, averages or other statistics
Summary of the rows
Year
1973
M
500
F
99
Both
Sexes
600
1970
580
87
670
1968
1966
460
260
89
71
550
330
Mean
430
86
520
Summary of the columns
10
Tables
2. Compare numbers in columns
Difficult to compare numbers in rows
Compare numbers in columns
23 42 34 109 87 42 27 98 114 75
1st improvement:
Right-justify numbers vertically
23
42
34
109
87
42
27
98
114
75
2nd improvement:
Sort numbers
11
23
27
34
42
42
75
87
98
109
114
Tables
3. Arrange key data by magnitude
Organize data by magnitude
Exposure
Cases
(1000s)
Rate
A
11
B
Exposure
Cases
(1000s)
Rate
2.9
B
6
9.9
06
9.9
C
34
5.4
C
34
5.4
A
11
2.9
None
27
2.3
None
27
2.3
Which is the most important column you would use to sort the table?
12
Tables
4. Align numbers by decimal
Align columns by decimal
Keeping the zeros or not is a question of
personal style
23
42
34
10.9
8.7
42
27
9.8
114
75
13
23.0
42.0
34.0
10.9
8.7
42.0
27.0
9.8
114.0
75.0
Tables
Example of one way table:
Data tabulated by one variable
Age distribution of a sample of
100 villagers
Age group (years)
Number
0-4
19
5-14
25
15-44
40
45+
16
Total
100
14
Tables
Example of two way table:
Data tabulated by two variable
Age and sex distribution of a sample of 100 villagers
Age group (years)
Male
Female
Number
0-4
10
9
19
5-14
12
13
25
15-44
20
20
40
7
9
16
49
51
100
45+
Total
15
Tables
Classical table of incidence by age and sex
Incidence of cholera by age and sex,
Kachua, West Bengal, India, 2004
Population
Age group
(years)
Sex
Total
Incidence per
thousand
Cases
0-4
129
15
116
5-14
210
18
86
15-29
383
13
34
30-44
334
8
24
45-59
159
1
6
60+
99
0
0
Male
666
28
42
Female
648
27
42
1,314
55
42
16
Use one graph to get one general
idea across
•
•
•
•
•
•
Don’t use a graph if there is nothing to say
Frame the idea to communicate
Identify the graph that matches this idea
Eliminate unnecessary information
If there are two ideas, use two graphs
Add a title with time, place and person
information
17
Graphs
Proportion (%)
Proportion of eligible patients whose
blood slides were examined for malaria,
Dhenkanal district, Orissa, 1996-2002
16
14
12
10
8
6
4
2
0
Is the graph useful?
1996
1997
1998
1999
2000
2001
2002
Years
18
Graphs
Keep the ink-to-data ratio low
• All elements on a graph must be justified
• Eliminate distracting, non-essential elements





Secondary axis
Gridlines
3-D effects
Bordering lines
Etc…
19
Graphs
Dracunculiasis rates, India, 1984-2000
(High ink to data ratio)
4000039792
35000
30000
30950
25000
23070
Number of cases20000
17031
15000
12023
10000
7881
5000
4798
20
2000
1998
1996
Year
1994
2185
1081
755371
60 9 0
0 0 0
1992
1990
1988
1986
1984
0
Graphs
Dracunculiasis rates, India, 1984-2000
(Simpler, better, low ink-to-data ratio)
45000
40000
Number of cases
35000
30000
25000
20000
15000
10000
5000
0
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
21
Year
Graphs
Choosing a type of graph
22
Graphs
0
2000
2001
2002
23
2003
May
June
July
August
September
October
November
December
30
February
March
April
May
June
July
August
September
October
November
December
January
February
March
April
May
June
July
August
September
October
November
December
January
February
March
April
35
January
February
March
April
May
June
July
August
September
October
November
December
January
February
March
April
May
June
July
August
September
October
November
December
January
Incidence of malaria per 10,000
Line graph for time series
Malaria in Kurseong block, Darjeeling
District, West Bengal, India, 2000-2004
45
40
Incidence of malaria
Incidence of Pf malaria
25
20
15
10
5
2004
Months
Graphs
Histogram to display a frequency
distribution
• Graphic representation of the frequency distribution
of a continuous variable
• Rectangles drawn in such a way that their bases lie
on a linear scale representing different intervals
• Areas are proportional to the frequencies of the
values within each of the intervals
• No spaces between columns
• No scale breaks
• Equal class intervals
• Epidemic curve is an example of histogram with
time on the x axis
24
Graphs
Histogram
Urinary iodine excretion status, 24 N
Parganas, West Bengal, India, 2004
Percentage
80
60
40
20
0
0-19.9
20-49.9
50-99.9
100-300
> 300
Urinary Iodine Excretion levels (µg/L)
25
Graphs
Epidemic curve
90
80
70
60
50
40
May
June
July
Week of onset
26
August
1st week
4th week
3rd week
2nd week
1st week
4th week
3rd week
2nd week
1st week
4th week
2nd week
1st week
4th week
3rd week
2nd week
10
0
3rd week
30
20
1st week
Number of cases
Acute hepatitis by week of onset in 3
villages, Bhimtal block, Uttaranchal, India,
July 2005
September
Graphs
Proportions of a total presenting
selected characteristics
• Breakdown of a total in proportions:
 Pie chart
• Breakdown of more than one total into
proportion:
 Juxtaposed bar charts cumulated to 100%
27
Graphs
Pie chart for the breakdown of a total in proportions
Types of unintentional injuries,
Tiruchirappalli, Tamil Nadu, India, 2003
Incidence:
9.6 per 100 person-month
(95% C.I. 8-11
Minor injuries
35%
Road
10%
Fall
32%
Burns 28
7%
Bites
16%
Graphs
Cumulated bar chart for the breakdown
of more than one total in proportions
Proportion (%)
Estimated and projected proportion of
deaths due to non-communicable
diseases, India, 1990-2010
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Injuries
Communicable
diseases
Non communicable
diseases
1990
2000
Year
29
2010
Graphs
Comparing proportions
• No logical order: Horizontal bar chart
 Sort according to decreasing proportions
• Logical order: Vertical bar chart
30
Graphs
Horizontal bar chart
Causes of non vaccination as reported by the
mothers, Bubaneshwar, Orissa, India, 2003
Lack of awareness
Child sick
Irregularity by health staff
Lack of motivation
Lack of time
Lack of facility
Lack of money
0%
India FETP
20%
40%
31
60%
80%
100%
Graphs
Vertical bar chart
Prevalence of hypertension by age and
sex, Aizawl, Mizoram, India, 2003
70
60
%
50
40
Male
30
Female
20
10
0
30-39
40-49
50-59
60-69
70 +
Age group (years)
32
Graphs
Maps
• Use maps to display information by place
 Do not use tables!
• Two types of maps:
 Spot maps
 Incidence maps
• Use a key
• Add a title with time, place and person
information
33
Maps
Drawing a spot map during an
outbreak investigation
• Rough sketch of the
setting of an outbreak
• One dot = One case
• Other locations of
potential importance
are also recorded
• Does not adjust for
population density
34
Maps
Spot map - Does not adjust for population density
Cholera cases by residence, Kanchrapara,
N-24 Parganas, West Bengal, India, 2004
35
Maps
An incidence map adjusts
for population density
• List the cases
• Regroup cases by location for which
population denominator is available
 Look up census data
• Divide the number of cases by the population
denominator
• Choose gradients of colours to represent
increasing levels of prevalence
36
Maps
Incidence map - Adjusts for population density
Cholera attack rate and water supply,
Sirunavalur, Tamil Nadu, India, 2002
Old well used only
in the summer
Attack rate by area
0-5%
Reddiar street
5 –10 %
PL street
> 10 %
Main road
Water tank filled
with well water
Colony
Main road
Main road
Centre east
Muthuraja
37
Maps
Preparing an incidence rate map:
What you will need
•
•
•
•
•
•
•
A hardcopy of your map
A transparency
Cello tape
Permanent markers
Computer
Drawing software
Incidence by geographical area
38
Step 1: Place transparency on the hardcopy of map
to draw map with permanent marker
39
Step 2: Stick the transparency on the screen with cello
tape and follow the guide to draw map with the mouse
in a drawing software
40
Step 3: Remove the transparency and edit the map in
the drawing software
41
Step 4: Filling the map with data
• Have a table of incidence by area
• Rank the areas by increasing level of
incidence
• Sort the areas in four groups in which there
is about the same number of area
 Add a fifth group if needed for incidence = 0
• Assign a colour per group
• Draw the map
42
Rate of disease X by country, South East Asia
WHO region, 200X
Yearly incidence per 100,000
0
0-19
20-49
50-99
100+
Using colours in maps
• The cold / warm scale
 Represents violent contrasts
• Increasing density in one colour
 Represents increasing levels of magnitude
• Complementary colours
 Use equivalent intensity
 Represents unrelated notions
44
Maps
Take home messages
1. Choose whether you want to represent an
overall message (Analogical) or whether
you want to describe detailed data (digital)
2. Present analyzed data in tables with
summary rows and columns
3. Display general ideas in graphs that carry
one single message
4. Use maps to display information by place
45