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 non buyers of a product are of interest. One classic study conducted by Shuchman and Riesz (Journal of Marketing Research) was aimed at characterizing the purchasers and non purchasers 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 non purchasers. A similar study used independent random samples of size 20 and yielded the data shown in the following table on the age of the householder primarily responsible for buying toothpaste.
a. Do the data present sufficient evidence to conclude there is a difference in the mean age of purchasers and non purchasers? Use α = .10.
b. What assumptions are necessary in order to answer part a?
c. Find the observed significance level for the test and interpret its value.
d. Calculate and interpret a 90% confidence interval for the difference between the mean ages of purchasers and non purchasers.

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Purchasers Nonpurchasers 34 35 23 44 52 46 28 22 44 33 55 63 28 48 28 34 33 52 45 31 60 54 53 58 41 32 34 49 50 45 52 52 66 35 25 48 29 59 1 3 5 59 61