Do chief executive officers of large corporations in different industries typically earn disparate annual salaries? Consider the data in the file P2_13.XLS, which came from a recent survey of chief executive officers of the nation’s 350 biggest businesses (The Wall Street Journal, April 9, 1998). In particular, we seek to discover whether significant differences exist between the mean levels of 1997 salaries earned by executives of Technology companies and those of each of the other seven company types. For instance, is the difference between the mean 1997 salaries of executives from Technology and Basic Materials companies significant?

a. Before conducting these hypothesis tests, perform a test for equal population variances for each pair of company types. For each pair, report a p-value and interpret it.

b. Based on your conclusions in part a, which test statistic should be used in performing a test for the existence of a difference between population means in each pair?

c. Gven your conclusions in part b, perform a test for the existence of a difference in mean annual CEO salaries. For each pair of company types, report a p-value and interpret its meaning.