Chapter 15, Problem 23P

To determine

1. Conversion of 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.
2. Square of the value of the point-biserial correlation to obtain $r^2.$
3. The $t$ test in chapter 10 produced $t=3.57$ with $df=16$. Use the equation on p. 518 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.