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Tables, graphs, and diagrams

Tables, graphs, and diagrams

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Tables, graphs, and diagrams

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  1. Tables, graphs, and diagrams Barbara SchimmerJurmala, Latvia, 2006 Based on EPIET material

  2. Contents • Use of tables, graphs and graphics • Graphics in descriptive epidemiology • describe • Graphics in analytical epidemiology • compare • Designing graphics

  3. Background

  4. Purpose Description Time Place Person Clinical features Comparison Odds ratios Relative risks Methods Surveillance Outbreakinvestigations Other studies:clinical epidemiologyfield trialsexperimental epidemiology Epidemiology

  5. Process data Organisetriage, cleaning Summariseaggregate Explore trends relationships errors Present data Communicate Paper Poster Screenstatic  animated Use of data tables and graphics?

  6. Paper Time unlimited Repetition Details notes? White, grey and black Screen Time < 1 min No repetition Less details Colours possible Paper vs. screen

  7. Tables, graphics, and diagrams • Self-explanatory • Simple! • Title (what, who, where, when) • Define abbreviations and symbols • Note data exclusions • Reference the source

  8. Time

  9. The epidemic curve 1

  10. 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 caseEasy to make in Excel

  11. The arithmetic-scale line graph 1

  12. 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

  13. The semilogarithmic-scale line graph 1

  14. 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

  15. 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

  16. Place

  17. The one-variabletable

  18. The spot map Figure 1. Cases of meningococcal disease in Dublin 1998 by place of residence. 1 dot = 1 case

  19. The area dot (or dot density) map Figure 2. Cases of meningococcal disease in Dublin 1998 by area of residence. 1 dot = 1 case

  20. The area map Figure 3. Incidence rate (per 100,000) of meningococcal disease in Dublin 1998 by area of residence.

  21. Person

  22. The two-variable table

  23. Grouped bar chart

  24. Stacked bar chart

  25. Component bar chart

  26. 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

  27. Pie chart

  28. Clinical features

  29. Table

  30. Birth weight of 36217 newborns

  31. Anything wrong with the distribution ?

  32. Anything else than the relation ?

  33. Comparison

  34. The 2x2 table for a cohort study

  35. The 2x2 table for a case control study

  36. Table from a case control study

  37. Design

  38. Think data-ink Every bit of ink should have a reason

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

  40. Standard symbols in tables

  41. Standard symbols in tables

  42. Summary • Use of graphics Explore and present • PresentationPaper 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!