Slides for lecture on basic graph types for a statistics class.

1. Chapter 2 and Infographics Project Graphs: Good, Bad & Ugly

2. A visual presentation of data Relationships & comparisons are visual Less daunting to some than tables of numbers Allows some artistry and creativity Accuracy is important Style of graph must match Scale (level) of measurement of the variable(s) Nature of this particular data set Purpose of a Graph

4. Category values labeled

5. Title for graph

6. Data bars proportional to number of cases in data

7. Balanced

8. Maintains scale

9. No “chart junk”

10. Not complicated

12. Area of bars combined is 100% Area of each bar is proportional to its percent of total Bars do not touchbecause categoriesare discrete. Many variations; this is the most simple. BAR CHART: the Good

13. The Bad:design hides trends or data

14. PICTOGRAPH: the Good bars constructed of equal size simple icons

15. PICTOGRAPH: the Ugly Elements of unequal size Just heads of some kids All children are playing except those from China – subtle racism

16. BAR CHART – problems to consider:area, color – & why is that jogger there?

17. Practice: How many problems can you see in this graph?

18. PIE CHART: the Acceptable Area of pie = 100% Wedge is proportional to percentage of cases Labels show count or percent Ten slices is the maximum to remain clear & readable.

19. PIE CHART: the Badcharts confuse or obscure the pattern in the data

20. What can you detect in this old graph?

21. Graphs for Continuous Data (sometimes used for Ordinal data) Graph shows continuity of the construct Histogram: bars that touch at real limits Line graph: covers range (a.k.a. Frequency Polygon) Horizontal axis goes from low to high Intervals shown for Interval or Ratio data Some ordinal data also graphed this way(e.g., strongly agree, agree, slightly agree, etc)

22. Bar width is a rangeof scores or the reallimits of scores. Ranges equal width Labels show mid-point or real limits Low scores on left, high scores on right HISTOGRAM: the Good

23. HISTOGRAM: the Bad Ranges of data Unequal & indeterminate Spacing of “bars” is unequal. Water, sky, umbrella detract from graph

25. Lowest categories are on the right, not left.

26. Intervals of income are unequal/indeterminate.

28. LINE GRAPH: the Bad Why is the headline “Steady growth” for this graph? Hint: check the axis values If it is growth, is it steady ? Hint: how did each of the three variables change from 1988 to 1989.

29. Modern graphs have more options The Future of Food. (2008) WiredMagazine 16:11

30. Chapter 2 and Infographics Project Graphs: Good, Bad & Ugly