Making Graphs

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Making Graphs - PowerPoint PPT Presentation

Making Graphs. The Basics … Graphical Displays Should:. induce the viewer to think about the substance rather than about the methodology, graphic design, the technology of the graphic production, or something else avoid distorting what the data have to say

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Making Graphs

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1. Making Graphs

2. The Basics … Graphical Displays Should: • induce the viewer to think about the substance rather than about the methodology, graphic design, the technology of the graphic production, or something else • avoid distorting what the data have to say • present many numbers in a small spaceContinued...

3. The Basics … Graphical Displays Should: (2) • make large data sets coherent • encourage the eye to compare different pieces of data • serve a clear purpose • be closely integrated with the statistical and verbal descriptions of a data set.

4. Lie Factor • Lie Factor = size of effect shown in graphic size of effect in data • Greater than 1.05% or less than .95% indicates substantial distortion, far beyond minor inaccuracies in plotting.

5. NYT: Fuil economy “graph”

6. The eye perceives area, not height

14. Chartjunk • What is it?Anything that doesn’t NEED to be included in the chart. • To clean-up chartjunk, watch your data-ink ratio. “Data-ink is the non-erasable core of a graphic, the non-redundant ink arranged in response to a variation in the numbers represented.” Data-ink ratio = data-ink total ink used to print the graphic

15. William Playfair (1759-1823) Inventor of: • Line graph • Bar graph • Pie chart

17. Imports and exports of Scotland

18. Playfair: area of countries (circles), population (left line seg.) and tax revenue (right line seg.).

19. U.S. age pyramids, 1874

20. Minard's Napoleon's March to Moscow

21. Tufte principles: • Show Data • Focus on Content instead of graphic production • Avoid Distorting what Data has to say • Make Large Data Sets Coherent • Encourage Eye to Compare Different Pieces of Data • Reveal Data at several Levels of Detail • Closely integrate Statistical and Verbal Descriptions

22. Line Graph • x-axis requires quantitative variable • Variables have contiguous values • familiar/conventional ordering among ordinals • Bar Graph • comparison of relative point values • Scatter Plot • convey overall impression of relationship between two variables • Pie Chart • Emphasizing differences in proportion among a few numbers

23. Bar charts • Best for comparing different things during the same time period • Neither the bars nor the axis should be interrupted • Axis should usually include zero (some exceptions) • Avoid 3-D effects, can be misleading

24. Line graphs • Best for showing change over time • Can indicate trends • Use a different color and symbol for each line • Avoid too many lines • When to use log scale

25. Percent of Persons Aged 65+ Residing with their Own Children aged 18+: United States 1850-2000 Labeling: Title Labeling: lines Height/width should be about 3:4 (same as old-fashioned TV

26. Percent of the Labor Force Employed in Agriculture, United States, 1800-2000

27. Figure 1: Percent of elders in intergenerational families Too many lines!

28. Brazil Colombia Venezuela Chile Ecuador Costa Rica Mexico Married Female Labor Force Participation in Latin America (age 18 to 65) 50 45 40 35 30 Percent in Labor Force 25 20 15 10 5 0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

29. 70 60 50 40 Percent in Labor Force 30 20 10 0 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Married Female Labor Force Participation: Latin America and U.S. (age 18 to 65) United States Latin America

30. Brazil Colombia Venezuela Ecuador Chile Costa Rica Mexico Married Female Labor Force Participation: Latin America and U.S. (age 18 to 65) 70 United States 60 50 40 Compare Latin America to U.S. 40 years ago Percent in Labor Force 30 20 10 0 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

31. Married Female Labor Force Participation: Mexican-born Women, 1970-2000 70 60 Mexican-born Women in United States 50 40 Percent in Labor Force 30 Women in Mexico 20 10 0 1970 1975 1980 1985 1990 1995 2000

32. Percent deviation in intergenerational coresidence of each occupational group from nonfarm average: Younger generation

33. IPUMS Graph from “A Century of Women in Science and Engineering,” History Day project by Abby Norling- Ruggles, age 12