Question

1. A psychologist wants to determine if an ad campaign aimed at increasing condom use among college students is effective at making existing attitudes toward condom use more positive. Attitudes toward condom use were measured in a sample of 8 participants during a baseline period, before the ad campaign began. Attitudes toward condom use were measured again six months into the campaign. Participants' pre- and post-attitude scores on this measure are displayed in the table below. Ratings are based on a seven-point scale where higher numbers indicate more favorable attitudes toward condom use. Participant Pretest Posttest State the null and alternative hypotheses. Was this campaign successful? (Use the .05 level for significance) Interpret the result. What do your results tell you about the efficacy of the ad campaign?

Answer 1

Let us denote the difference

d = Pre-test score - Post-test score

Conclusion : There is sufficient evidence to conclude that ad campaign significantly increased condom use among college students.

Let ud denotes the population mean of difference. To test null hypothesis Ho Md =0.0 against alternative hypothesis H1 :Md < 0.0 Let d denotes the sample mean of difference, sd denotes the sample standard deviation of difference and n denotes the sample size. Here, T = -1.8750, să = 1.2679, sa = 1.1260, n = 8 The test statistic can be written as: t- vn(d – 0.0) sd which under Ho follows a t distribution with n-1 df. We reject Ho at 0.05 level of significance if P-value < 0.05 or if tobs <-t0.05,n-1 Now, The value of the test statistic = -4.709894 associated degrees of freedom = 7 The critical value = -1.894579 P-value = P(ty <-4.709894) = 0.001092 Since p-value < 0.05 and tobs < tcritical = -1.894579, so we reject Ho at 0.05 level of significance Hence, we can conclude that scores on the second group is significantly higher than first group.