Tables, graphs, and diagrams

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Tables, graphs, and diagrams

• Preben Aavitsland
• Vladimír Príkazský
• Viviane Bremer

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Tables, graphs and diagrams.

• organise
• summarise
• display
• ...data from outbreaks, surveillance and studies

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Uses of tables, graphs and diagrams

• Effective presentation
• to the professionals
• to the public
• Easy interpretation
• Visual examination
• Analysis

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Paper vs. screen

• Paper
• Time unlimited
• Repetition
• Details
• White, grey and black

• Screen
• Time lt 1 min
• No repetition
• Less details
• Colours possible

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Tables, graphs, and diagrams

• Self-explanatory
• Simple!
• Title
• what, who, where, when
• Define abbreviations and symbols
• Note data exclusions
• Reference the source

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Type of variables

• Quantitative
• Discrete
• counts, dates, cases,...
• Continous
• height, Hb, .

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Type of variables

• Qualitative
• Dichotomous
• sex, ill/not ill, .
• Nominal
• religion, nationality, eye colour,...
• Ordinal
• social class, cancer stage, .

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Tables
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Types of commonly used tables

• One-variable tables
• Frequency distribution
• Multivariable tables
• Contingency tables
• 2x2 tables

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Group ERS Group KLO Group MGI Group NHO Group NEA Group KLN
Day 1-2 Day 1-2 Day 1-2 Day 3-4 Day 3-4 Day 3-4
Factory Atada NDPH 13 1245 53 3467 3462 2425
Factory Seuda 457 2351 6589 9i0 569 43
Factory Desda 111 (56) 43 (96) 35 (97) 46 (53) 56 (75) 567 (42)
Factory Rioja 1 1 0 3
Mean age 23 34 23 45 23 32
Travel hours 64 45 56 678 89 890
H C AB level 67 70 890 4356 56 76
HIV 54 56 678 567 890 9080
Primary school 345 34 45 e65 56 78
Secondary school 234 54 65 568 76 878

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Tab 6. Distribution of cases of salmonellosis
(n65) by age group. Hospital A, Dublin, August
2006
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Table 9. Gonorrhoea by age-group and sex, Norway,
2005
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Tab. IV Fish consumption and gastro-intestinal
illness among customers at Uncle Mikes Fish
Chips, Berlin, 2005
Ill Total Attack rate Relativerisk
Ate fish 42 58 72.4 9.3 (3.9-22)
Did not eat fish 5 64 7.8 Ref
Total 47 122 39
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Tab. IV Gastrointestinal illness and fish
consumption among customers at Uncle Mikes Fish
Chips, Berlin, 2005
Cases Controls Total OR (CI95)
Ate fish 34 20 54 13 (5.3-33.0)
Did not eat fish 8 62 70 Ref
Total 42 82 124
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Table from a case control study (paper) Tab. IV
Gastrointestinal illness and fish consumption
among customers at Uncle Mikes Fish Chips,
Berlin, 2005, n124 (2 cases were excluded)
Cases n42 Controls n82 Total n124 OR (CI95)
Swordfish 34 20 54 13.2 (5.3-33.0)
Paella 8 62 70 0.1 (0.01-0.95)
Chicken 12 23 35 1.0 (0.4-1.9)
Flan caramel 20 40 60 0.9 (0.2-2.9)
Crema catalan 10 22 32 0.3 (0.1-1.4)
Lemon tarte - 80 120 .
explanation of symbols - we measured, no
case in this category, we cant say that it is
0 . we measured, but we cant calculate the
average of 1 case
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In tables...

• Labels for rows and columns
• Totals for rows and columns, usually
• Units of measurements
• Max five variables
• Horizontal lines OK, vertical not

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Graphs Diagrams
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Types of commonly used graphs

• Line graph
• Arithmetic scale line graph
• Semi-logarithmic scale line graph
• Histogram
• Epidemic curve

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The arithmetic-scale line graph 1
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The arithmetic-scale line graph 2

• For time series
• Show actual changes in magnitude
• X-axis time
• Y-axis incidence (or number) of cases
• Start at 0
• Breaks possible, clearly marked

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The semilogarithmic-scale line graph 1
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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

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The epidemic curve 1 Cases of salmonellosis
(n65) by date and time of onset of illness.
Hospital A, Dublin, August 2006
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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

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In graphs...

• Labels for axes, scales and legends
• Legends or keys if gt1 variable
• Scale divison, appropriate scale
• Units of measurements in title
• No grid, no numbers
• No 3D

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Types of commonly used charts

• Charts based on length
• Bar charts(horizontal, vertical, grouped,
  stacked)
• Charts based on proportion
• Component bar chart
• Pie chart

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Grouped bar chart
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Stacked bar chart
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Component bar chart
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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

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Pie chart
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The area dot (or dot density) map
Figure 2. Cases of meningococcal disease in
Dublin 2006 by area of residence. 1 dot 1 case
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The spot map
Figure 1. Cases of meningococcal disease in
Dublin 2006 by place of residence. 1 dot 1 case
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The area map
Figure 3. Incidence per 100,000 of meningococcal
disease in Dublin 2006 by area of residence.
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Think data-ink

• Every bit of ink should have a reason

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Designing graphics

• Show the data
• Use ink for the data
• Remove unnecessary ink
• Remove gimmicks
• No 3D
• Careful with colours

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Summary

• Use graphics to explore and present data
• Think of difference between paper and screen
• Think of your message and choose the graph type
  accordingly
• Save your ink!