FILE In the United States, baseball has always been a favorite pastime and is rife with statistics and theories. While baseball purists may disagree, to an applied statistician no topic in baseball is too small or hypothesis too unlikely. In a recent paper, researchers at Wayne State University showed that major-league players who have nicknames live 21/2 years longer than those without them (The Wall Street Journal, July 16, 2009). Perhaps nicknames add to the self-esteem of a player. Consider the following portion of data on the lifespan (years) of a player and a nickname dummy that equals 1 if the player had a nickname and 0 otherwise; the complete data set can be found on the text website, labeled Nicknames.

Years Nickname 74 1 62 1

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64 0

a. Create two subsamples, with one consisting of players with a nickname and the other one without a nickname.

Calculate the average longevity for each subsample.

b. Estimate a linear regression model of Years on the Nickname dummy variable. Compute the predicted longevity of players with and w ithout a nickname.

c. Conduct a one-tailed test at a 5% level to determine if players with a nickname live longer.