Do nice guys finish first or last? Refer to the Nature (Mar. 20, 2008) study of the use of punishment in cooperation games, Exercise 11.22

(p. 625). Recall that college students repeatedly played a version of the game “prisoner’s dilemma”

and the researchers recorded the average payoff (y) and the number of times punishment was used (x) for each player.

A negative correlation was discovered between x and y.

a. Give the null and alternative hypotheses for testing whether average payoff and punishment use are negatively correlated.

b. The test, part

a, yielded a p-value of .001. Interpret this result using x = .05.

c. Does the result, part

b, imply that increasing punishment causes your payoff to decrease? Explain.