Injuries to Major League Baseball players have been increasing in recent years. For the period 1992 to 2001, league expansion caused Major League Baseball rosters to increase 15%. However, the number of players being put on the disabled list due to injury increased 32% over the same period (USA Today, July 8, 2002). A research question addressed whether Major League Baseball players being put on the disabled list are on the list longer in 2001 than players put on the disabled list a decade earlier.
a. Using the population mean number of days a player is on the disabled list, formulate null and alternative hypotheses that can be used to test the research question.
b. Assume that the following data apply:

What is the point estimate of the difference between population mean number of days on the disabled list for 2001 compared to 1992? What is the percentage increase in the number of days on the disabled list?
c. Use α = .01. What is your conclusion about the number of days on the disabled list? What is the p-value?
d. Do these data suggest that Major League Baseball should be concerned about the situation?

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2001 Season 1992 Season Sample size Sample mean Sample standard deviation 45 12 = 38 60 days s, = 18 days 51 days s, = 15 days