Problem 13 in Chapter 10 presented data demonstrating that handling money can reduce the perception of pain. In the study, one group counted money and another group counted blank pieces of paper. After the counting task, each participant dipped a hand into very hot water and rated how uncomfortable it was.

a. Convert the data from this problem into a form suitable for the point-biserial correlation (use 1 for the money and 0 for the plain paper), and then compute the correlation.

b. Square the value of the point-biserial correlation to obtain r 2

.

c. The t test in Chapter 10 produced t 5 3.57 with df 5 16.

Use the equation on page 448 to compute the value of r 2

directly from the t statistic and its df. Within rounding error, the value of r 2

from the equation should be equal to the value obtained from the point-biserial correlation.