solution

Study of recall of TV commercials. Refer to the Journal of Applied Psychology (June 2002) completely randomized design study to compare the mean commercial recall scores of viewers of three TV programs, presented in Exercise 9.28 (p. 544). Recall that one program had a violent content code (V) rating, one had a sex content code (S) rating, and one was a neutral TV program. Using Tukey’s method, the researchers conducted multiple comparisons of the three mean recall scores.

a. How many pairwise comparisons were made in this study?

b. The multiple comparison procedure was applied to the data and the results are shown in the Minitab printout at the top of the next page. An experimentwise error rate of .05 was used. Locate the confidence interval for the comparison of the V and S groups. Interpret this result practically.

c. Repeat part b for the remaining comparisons. Which of the groups has the largest mean recall score?

 d. In the journal article, the researchers concluded that “memory for [television] commercials is impaired after watching violent or sexual programming.” Do you agree?

Exercise 9.28

Study of recall of TV commercials. Do TV shows with violence and sex impair memory for commercials? To answer this question, lowa State researchers conducted a designed experiment in which 324 adults were randomly assigned to one of three viewer groups of 108 participants each (Journal of Applied Psychology, June 2002). One group watched a TV program with a violent content code (V) rating, the second group viewed a show with a sex content code (S) rating, and the last group watched a neutral TV program with neither a V nor an S rating. Nine commercials were embedded into each TV show. After viewing the program, each participant was scored on his or her recall of the brand names in the commercial messages, with scores ranging from 0 (no brands recalled) to 9 (all brands recalled). The data (simulated from information provided in the article) are saved in the accompanying file. The researchers compared the mean recall scores of the three viewing groups with an analysis of variance for a completely randomized design.

a. Identify the experimental units in the study.

b. Identify the dependent (response) variable in the study.

c. Identify the factor and treatments in the study.

d. The sample mean recall scores for the three groups were _v = 2.08, _s = 1.71, and _Neutral = 3.17. Explain why one should not draw an inference about differences in the population mean recall scores on the basis of only these summary statistics.

e. An ANOVA on the data yielded the results shown in the Minitab printout below. Locate the test statistic and p-value on the printout.

f. Interpret the results from part e, using  = 0.01. What can the researchers conclude about the three groups of TV ad viewers?

g. Check that the ANOVA assumptions are reasonably satisfied.