5Exceptional CasesThe correlation coefficient r is less useful in case there are outliers.Moreover, r measures linear association, not association in general.
6Ecological Correlation In one study, a scatter diagram was shown showing the relationship between the rate of smoking per capita and the rate of deaths from lung cancer in eleven countries.The correlation between these eleven pairs of rates was 0.7.Comment on this data.
7Ecological Correlation Correlations based on rates or averages can be misleading.For example: in each country, there is a lot of spread around the averages.Replacing the people by the country’s average eliminates the spread, and gives the misleading impression of tight clustering.
9Suicide and LiteracyA sociologist is studying the relationship between suicide and literacy in nineteenth-century Italy. He has data for each province. The correlation is 0.6.Does this give a fair estimate of the strength of the association between literacy and suicide?
10Association is not Causation For school children, shoe size is strongly correlated with reading skills.In the Great Depression, better educated people tended to have shorter spells of unemployment. Does education protect you against unemployment?
11Reading and the TVStudies have found a negative association between hours spent watching television and scores on reading tests.Does watching television make people less able to read?
13True or False?If r = -0.80, below average values of the dependent variable are associated with below-average values of the independent variable.If y is usually less than x, the correlation coefficient between x and y will be negative.
14Height and Weight, Again An investigator collected data on heights and weights of college students.Suppose the correlation coefficient between height and weight for the men was about 0.60; for the women, about the same.What happens to the correlation coefficient if you take the men and women together?
15Math SAT scoresETS computed the average score for each of the 51 states, and the percentage of the high-school seniors in that state who took the test. The correlation between these two variables was equal to –0.86.True or false: test scores tend to be lower in the states were a higher percentage take the test.
16Math SAT scoresIn New York, the average score was only 471; in Wyoming, the average was 507.True or false: the data show that on average, the schools in W. are doing a better job at teaching math than the schools in NY.
17Verbal SATETS computed the average Verbal SAT score for each state, as well as the average Math SAT score. The correlation between these 51 pairs of averages was Would the correlation between the Math SAT and Verbal SAT computed from the data on all the individual test takers be larger than 0.97, about 0.97, or less than 0.97?