9. Problem 22 in Chapter 9 described a study reporting that a good sense of humor can have a significant effect on how people judge the attractiveness of a potential romantic partner. In the study, female college students read brief descriptions of a man. For one group, the description said that he had a great sense of humor, and for another group, it said that he had no sense of humor. After reading the description, the participants were asked to rate the attractiveness of the man from 1 (very unattractive) to 7 (very attractive).

a. The n = 16 females who read the “great sense of humor” description gave an average attractiveness rating of M = 4.53 with a standard deviation of 1.04. Use the sample to compute an 80% confidence interval for the population mean rating.

b. The n = 16 females who read the “no sense of humor” description gave an average attractiveness rating of M = 3.30 with a standard deviation of 1.18. Use the sample to compute an 80% confidence interval for the population mean rating.

c. Use the two samples to make an 80% confidence interval estimate of the mean difference in rated attractiveness for the two descriptions. Note:

Because the samples are the same size, the pooled variance is the average of the two sample variances.