data presentation tables, graphs and maps integrated disease surveillance programme (idsp) district...
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Data presentation Tables, graphs and maps
Integrated Disease Surveillance Programme (IDSP) district surveillance
officers (DSO) course
2
Outline of the session
1. Analogical versus digital information
2. Tables3. Graphs 4. Maps
3
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 amDigital and analogical information
4
Nu
mb
er
of c
ase
s
Month of onset
Cases of monkeypox by month of onset, Katako-Kombe, Zaire,
1996-1997
0
5
10
15
20
25
30
Feb Mar Apr May Jun1996
Jul Aug Sep Oct Nov Dec Jan1997
Feb
Secondary cases
Primary cases
Example: Analogical display of information (Graph)
WHO-CDC
Digital and analogical information
5
Cases of Monkeypox by month of onset, Katako-Kombe, Zaire,
1996-1997Primary cases Secondary cases
Feb-96 2 0Mar-96 0 3Apr-96 2 2May-96 5 6Jun-96 0 5Jul-96 4 9Aug-96 3 23Sep-96 1 5Oct-96 1 2Nov-96 3 1Dec-96 0 0Jan-97 2 0Feb-97 1 9Total 24 65
Example: Digital display of information (Table)
Digital and analogical information
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Tables
• Presentation of detailed analyzed data
• Do not present raw data E.g., lists
• Present analyzed data with summary statistics
Tables
7
Column headings
Data
Footnotes
Title
Row headings
Typical table layout with components
8Tables
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
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Selected suggestions for data arrangement in tables
1. Summarize rows and columns2. Compare numbers in columns 3. Arrange key data by magnitude4. Align numbers by decimal
Tables
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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
1. Summarize rows and columnsSummarize rows and columns
with totals, averages or other statistics
Tables
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Compare numbers in columns
23 42 34 109 87 42 27 98 114 75
Difficult to compare numbers in rows
23 42 34109 87 42 27 98 114 75
1st improvement: Right-justify numbers
vertically 2327 34424275 87 98109 114
2nd improvement: Sort numbers
2. Compare numbers in columns
Tables
12
Organize data by magnitude
Exposure
Cases(1000s
) Rate
A 11 2.9
B 06 9.9
C 34 5.4
None 27 2.3
3. Arrange key data by magnitude
TablesWhich is the most important column you would use to sort the table?
Exposure
Cases(1000s
)Rate
B 6 9.9
C 34 5.4
A 11 2.9
None 27 2.3
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Align columns by decimal
23 42 3410.9 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
4. Align numbers by decimal
Tables
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Age distribution of a sample of 100 villagers
Example of one way table: Data tabulated by one variable
Age group (years)
Number
0-4 19
5-14 25
15-44 40
45+ 16
Total 100Tables
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Example of two way table: Data tabulated by two variable
Age group (years)
Male Female Number
0-4 10 9 19
5-14 12 13 25
15-44 20 20 40
45+ 7 9 16
Total 49 51 100
Age and sex distribution of a sample of 100 villagers
Tables
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Incidence of cholera by age and sex, Kachua, West Bengal, India, 2004
Population CasesIncidence per
thousand
Age group (years)
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
Sex Male 666 28 42
Female 648 27 42
Total 1,314 55 42
Classical table of incidence by age and sex
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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
Graphs
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Proportion of eligible patients whose blood slides were examined for malaria, Dhenkanal district, Orissa,
1996-2002
0
2
4
6
8
10
12
14
16
1996 1997 1998 1999 2000 2001 2002
Years
Pro
po
rtio
n (
%)
Is the graph useful?
Graphs
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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…
Graphs
20
Dracunculiasis rates, India, 1984-2000 (High ink to data
ratio)
Graphs
1984
1986
1988
1990
1992
1994
1996
1998
2000
39792
30950
23070
17031
12023
7881
4798
2185108175537160 9 0 0 0 0
0
5000
10000
15000
20000
25000
30000
35000
40000
Number of cases
Year
21
Dracunculiasis rates, India, 1984-2000 (Simpler, better,
low ink-to-data ratio)
Graphs0
5000
10000
15000
20000
25000
30000
35000
40000
45000
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
Year
Number of cases
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Choosing a type of graph
Graphs
23
Malaria in Kurseong block, Darjeeling District, West Bengal, India, 2000-2004
0
5
10
15
20
25
30
35
40
45
Janu
ary
Feb
ruar
y
Mar
chA
pril
May
June
July
Aug
ust
Sep
tem
ber
Oct
ober
Nov
embe
r
Dec
embe
rJa
nuar
yF
ebru
ary
Mar
chA
pril
May
June
July
Aug
ust
Sep
tem
ber
Oct
ober
Nov
embe
r
Dec
embe
r
Janu
ary
Feb
ruar
yM
arch
Apr
ilM
ayJu
neJu
lyA
ugus
t
Sep
tem
ber
Oct
ober
Nov
embe
r
Dec
embe
rJa
nuar
y
Feb
ruar
yM
arch
Apr
ilM
ay
June
July
Aug
ust
Sep
tem
ber
Oct
ober
Nov
embe
rD
ecem
ber
Janu
ary
Feb
ruar
yM
arch
Apr
il
May
June
July
Aug
ust
Sep
tem
ber
Oct
ober
Nov
embe
rD
ecem
ber
2000 2001 2002 2003 2004
Months
Inci
denc
e of
mal
aria
per
10,
000 Incidence of malaria
Incidence of Pf malaria
Line graph for time series
Graphs
24
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
Graphs
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0
20
40
60
80
0-19.9 20-49.9 50-99.9 100-300 > 300
Urinary Iodine Excretion levels (µg/L)
Pe
rce
nta
ge
HistogramUrinary iodine excretion
status, 24 N Parganas, West Bengal, India, 2004
Graphs
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Acute hepatitis by week of onset in 3 villages, Bhimtal block, Uttaranchal, India, July 2005
0
10
20
30
40
50
60
70
80
90
1st
wee
k
2nd
w
eek
3rd
we
ek
4th
wee
k
1st
wee
k
2nd
w
eek
3rd
we
ek
4th
wee
k
1st
wee
k
2nd
w
eek
3rd
we
ek
4th
wee
k
1st
wee
k
2nd
w
eek
3rd
we
ek
4th
wee
k
1st
wee
k
May June July August September
Week of onset
Num
ber
of c
ases
Epidemic curve
Graphs
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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%
Graphs
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Road10%
Fall32%
Bites16%
Burns7%
Minor injuries35%
Types of unintentional injuries, Tiruchirappalli, Tamil Nadu,
India, 2003
Incidence: 9.6 per 100 person-month
(95% C.I. 8-11
Pie chart for the breakdown of a total in proportions
Graphs
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Estimated and projected proportion of deaths due to non-communicable diseases,
India, 1990-2010
0%10%20%30%40%50%60%70%80%90%100%
1990 2000 2010
Year
Proportion (%)
Injuries
CommunicablediseasesNon communicablediseases
Cumulated bar chart for the breakdown of more than one total in proportions
Graphs
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Comparing proportions
• No logical order: Horizontal bar chart Sort according to decreasing proportions
• Logical order: Vertical bar chart
Graphs
31
Causes of non vaccination as reported by the mothers,
Bubaneshwar, Orissa, India, 2003
0% 20% 40% 60% 80% 100%
Lack of money
Lack of facility
Lack of time
Lack of motivation
Irregularity by health staff
Child sick
Lack of awareness
India FETP
Horizontal bar chart
Graphs
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0
10
20
30
40
50
60
70
30-39 40-49 50-59 60-69 70 +
Age group (years)
% Male
Female
Prevalence of hypertension by age and sex, Aizawl, Mizoram,
India, 2003
Vertical bar chart
Graphs
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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
Maps
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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
Maps
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Cholera cases by residence, Kanchrapara,
N-24 Parganas, West Bengal, India, 2004
Spot map - Does not adjust for population density
Maps
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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
Maps
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Cholera attack rate and water supply, Sirunavalur, Tamil
Nadu, India, 2002
Centre east
Valluva
r |street
Main road
PL street
Reddiar street
MuthurajaColony
0-5%
5 –10 %
> 10 %
Attack rate by areaOld well used onlyin the summer
Water tank filled with well water Main road
Main road
Incidence map - Adjusts for population density
Maps
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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
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Step 1: Place transparency on the hardcopy of map
to draw map with permanent marker
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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
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Step 3: Remove the transparency and edit the map in the drawing software
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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
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+
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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
Maps
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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