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Describing data with graphics and numbers

Describing data with graphics and numbers. Types of Data. Categorical Variables also known as class variables, nominal variables Quantitative Variables aka numerical nariables either continuous or discrete. Graphing categorical variables.

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Describing data with graphics and numbers

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  1. Describing datawith graphicsand numbers

  2. Types of Data • Categorical Variables • also known as class variables, nominal variables • Quantitative Variables • aka numerical nariables • either continuous or discrete.

  3. Graphing categorical variables

  4. Ten most common causes of death in Americans between 15 and 19 years old in 1999.

  5. Bar graphs

  6. Graphing numerical variables

  7. Heights of BIOL 300 students (cm) 165 168 163 173 170 163 170 155 152 190 170 168 142 160 154 165 156 177 173 165 165 175 155 166 168 165 180 165

  8. Stem-and-leaf plot

  9. Stem-and-leaf plot 0 0 0 0 0 3 3 5 7 0 3 3 5 5 5 5 5 5 6 8 8 8 2 4 5 5 6 2 19 18 17 16 15 14

  10. Frequency table

  11. Frequency table

  12. Histogram

  13. Histogram

  14. Histogram Frequency distribution

  15. Histogram with more data

  16. 50th percentile (median) 90th percentile

  17. Associations between two categorical variables

  18. Association between reproductive effort and avian malaria

  19. Association between reproductive effort and avian malaria

  20. Mosaic plot

  21. Grouped Bar Graph

  22. Associations between categorical and numerical variables

  23. Multiple histograms

  24. Associations between two numerical variables

  25. Scatterplots

  26. Scatterplots

  27. Evaluating Graphics • Lie factor • Chartjunk • Efficiency

  28. Don’t mislead with graphics

  29. Better representation of truth

  30. Lie Factor • Lie factor = size of effect shown in graphic size of effect in data

  31. Lie Factor Example Effect in graphic: 2.33/0.08 = 29.1 Effect in data: 6748/5844 = 1.15 Lie factor = 29.1 / 1.15 = 25.3

  32. Chartjunk Unnecessary or confusing visual elements IN CHARTS OR GRAPHS

  33. Say no to chartjunk!

  34. Needless 3D Graphics

  35. Summary: Graphical methods for frequency distributions

  36. Summary: Associations between variables

  37. Great book on graphics

  38. Describing data

  39. Two common descriptions of data • Location (or central tendency) • Width (or spread)

  40. Measures of location Mean Median Mode

  41. Mean n is the size of the sample

  42. Mean Y1=56, Y2=72, Y3=18, Y4=42

  43. Mean Y1=56, Y2=72, Y3=18, Y4=42 = (56+72+18+42) / 4 = 47

  44. Median • The median is the middle measurement in a set of ordered data.

  45. The data: 18 28 24 25 36 14 34

  46. The data: 18 28 24 25 36 14 34 can be put in order: 14 18 24 25 28 34 36 Median is 25.

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