The data relevant to Exercise 9.15 are the test scores and SAT-V scores for the 28 people in the group that did not read the passage. These data are

Exercise 9.15

In the study by Katz, et al., referred to previously, in which subjects answered questions about passages they had not read, the question arises as to whether there is a relationship between how the students performed on this test and how they had performed on the SAT-Verbal when they applied to college. Why is this a relevant question?

Interpret the results from Exercises 9.12–9.15.

Exercises 9.12–9.15

Why would you not feel comfortable computing a Pearson correlation on the data in Exercise 9.10?

Exercise 9.10

Down syndrome is another problem that psychologists deal with. It has been proposed that mothers who give birth at older ages are more likely to have a child with Down syndrome. Plot the data below relating age to incidence. The data were taken from Geyer (1991).

Plot a scatter diagram for the percentage of Down⁸ syndrome cases (Down / Births) as a function of age.

Exercise 9.13

One way to get around the problem you see in Exercise 9.12 would be to convert the incidence of Down syndrome to ranked data. Replot the data using ranked incidence and calculate the correlation. Is this a Spearman’s correlation?

Exercise 9.14

Do Exercise 9.13 using R. You can rank the data with ranked. data 5 rank(percent).

Exercise 9.15

In the study by Katz, et al., referred to previously, in which subjects answered questions about passages they had not read, the question arises as to whether there is a relationship between how the students performed on this test and how they had performed on the SAT-Verbal when they applied to college. Why is this a relevant question?

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Score 58 48 48 41 34 43 38 53 41 60 60 55 SAT-V 590 590 580 490 550 580 550 700 560 690 800 44 43 49 600 650 580 Score 47 33 47 40 46 53 40 45 SAT-V 660 590 600 540 610 580 620 600 39 47 50 53 560 560 570 630 46 510 620 53