The owner of a winery is wondering whether the average purchase of visitors to her winery differs according to age. She asks the cashiers to keep track of a random sample of purchases by customers in three age groups: under 30, 30-50, over 50. Because there is no good reason to ask a customer his or her age, the cashiers guess which age group a customer belongs to (and if they do not guess accurately, the research may not be helpful). Eventually, data from about 50 purchases made by customers in each of the age groups are collected. The Data Analysis output for Anova: Single Factor is shown opposite in Exhibit 11.19. At the 5% level of significance, is there evidence that customers in the different ages groups make different average purchases? You should already have checked conditions in Develop Your Skills 11.1, Exercise 2.

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Anova: Single Factor SUMMARY Groups Count Average Variance Under 30 30-50 Over 50 50 387.42 77.5684 652.9145 50 5983.54 119.6708 555.0899 50 663. 132.4674 625.7846 ANOVA Source of Variation P-value 2 41252.21 67.48684 1.61E-21 SS df MS Between Groups 82504.42 Within Groups 89855.66 147 611.263 Total 172360.1 149