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 2½ years longer than those without them (The Wall Street Journal, July 16, 2009). Consider the following portion of data on the lifespan (Years) of a player and a Nickname dummy variable that equals 1 if the player had a nickname and 0 otherwise; the entire data set, labeled Nicknames, can be found on the text website.

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 without a nickname.
c. Conduct a one-tailed test at a 5% level to determine if players with a nickname livelonger.

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Years Nickname 74