15. Problem 23 in Chapter 10 presented hypothetical data showing that elderly people who own dogs are significantly less likely to pay visits to their doctors than those who do not own pets. The independent-measures t test produced t 2.11 with df 11 and a value of r 0.288 (28.8%).

a. Convert the data from this problem into a form suitable for the point-biserial correlation (use 1 for the control group and 0 for the dog owners), and then compute the correlation.

b. Square the value of the point-biserial correlation to verify that you obtain the same r 2 value that was computed in Chapter 10.