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

6

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

9

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

10

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

11

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

13

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

14

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

15

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

16

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

17

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

18

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

19

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

22

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

25

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

26

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

27

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

28

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

29

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

30

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

32

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

33

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

34

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

35

Cholera cases by residence, Kanchrapara,

N-24 Parganas, West Bengal, India, 2004

Spot map - Does not adjust for population density

Maps

36

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

37

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

38

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

39

Step 1: Place transparency on the hardcopy of map

to draw map with permanent marker

40

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

41

Step 3: Remove the transparency and edit the map in the drawing software

42

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+

44

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

45

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