# 15.18 Research Questions

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15.18 Sixty-four students in an introductory college economics class were asked how many credits they had earned in college, and how certain they were about their choice of major. Research question: At α = .01, is the degree of certainty independent of credits earned? Let H0 = The degree of certainty is not independent of the credits earned and H1 = The degree of certainty is independent of the credits earned The Chi Square critical value is 13.26 Since 14.76 > 13.28, we reject the H0 and accept H1. Statistical evidence shows that the degree of certainty is independent of the credits earned. 15.22 A student team examined parked cars in four different suburban shopping malls. One hundred vehicles were examined in each location. Research…show more content…
15.28 Can people really identify their favorite brand of cola? Volunteers tasted Coca-Cola Classic, Pepsi, Diet Coke, and Diet Pepsi, with the results shown below. Research question: At α = .05, is the correctness of the prediction different for the two types of cola drinkers? Could you identify your favorite brand in this kind of test? Since it is a 2 × 2 table, try also a two-tailed two-sample z test for π1 = π2 (see Chapter 10) and verify that z2 is the same as your chi-square statistic. Which test do you prefer? Why? (Data are from Consumer Reports 56, no. 8 [August 1991], p. 519.) Chi Square: Let H0 = The correctness of prediction is independent of the cola type and H1 = The correctness of prediction depends upon the cola type There is no statistical evidence to suggest that the correctness of prediction is dependent on the cola type. Two-tail z- Test: H0: There is no difference between the abilities to identify the colas; that is, the correctness of prediction is independent of the cola type; that is, p1 – p2 = 0 Ha: There is a difference between the abilities to identify the colas; that is, the correctness of prediction depends upon the cola type; that is, p1 – p2 ≠