Children’s recall of TV ads. Refer to the Journal of Advertising (Spring 2006) study of children’s recall of television commercials, Exercise 9.17

(p. 477). You used a small-sample t test to test the null hypothesis H0: 1m1-m22 = 0, where m1 = mean number of ads recalled by children in the video-only group and m2 = mean number of ads recalled by children in the A>V group.

Summary statistics for the study are reproduced in the table.

The validity of the inference derived from the test is based on the assumption of equal group variances, i.e., s1 2

= s2 2 .

a. Set up the null and alternative hypothesis for testing this assumption.

b. Compute the test statistic.

c. Find the rejection region for the test using a = .10.

d. Make the appropriate conclusion, in the words of the problem.

e. Comment on the validity of the inference derived about the difference in population means in Exercise 9.17.

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Video-Only Group A Group n1 20 n2 20 X1 x = 3.70 X2 X = 3.30 $1 = 1.98 $22.13