In a recent study, a sample of college undergraduates looked at 2 graphs like those shown below. These graphs are identical in that (1) each shows the test scores earned by 100 students, (2) each mean score is 75, and (3) each distribution is symmetrical around a single mode. However, the variability of the scores in the graphs is different.
When asked to identify the graph with the larger variability, 50% of the undergraduates answered incorrectly. Can you tell which set of scores is more heterogeneous?
To see the answer (and to learn more about how variability shows up in simple graphs), go to http://www.amstat.org/publications/jse/v18n2/cooper.pdf