A large buyer of household batteries wants to decide which of two equally priced brands to purchase. To do this, he takes a random sample of 100 batteries of each brand. The lifetimes, measured in hours, of the batteries are recorded in the file P10_16.XLS. Before testing for the difference between the mean lifetimes of these two batteries, he must first determine whether the underlying population variances are equal.

a. Perform a test for equal population variances. Report a p-value and interpret its meaning.

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