Marketing strategists would like to predict consumer response to new products and their accompanying promotional schemes. Consequently, studies that examine the differences between buyers and nonbuyers of a product are of interest. One classic study conducted by Shuchman and Riesz (Journal of Marketing Research, Feb. 1975) was aimed at characterizing the purchasers and nonpurchasers of Crest toothpaste. The researchers demonstrated that both the mean household size

(number of persons) and mean household income were significantly larger for purchasers than for nonpurchasers.

A similar study utilized independent random samples of size 20 and yielded the data shown in the table on the age of the householder primarily responsible for buying toothpaste. An analysis of the data is provided in the SAS printout at the bottom of the page.

Purchasers I Nonpurchasers

a. Do the data present sufficient evidence to conclude there is a difference in the mean age of purchasers and nonpurchasers? Use a = .lo.

b. What assumptions are necessary in order to answer part a?

c. Find the observed significance level for the test on the printout, and interpret its value.

d. Calculate and interpret a 90% confidence interval for the difference between the mean ages of purchasers and nonpurchasers.