People tend to evaluate the quality of their lives relative to others around them. In a demonstration of this phenomenon, Frieswijk, Buunk, Steverink, and Slaets (2004) conducted interviews with frail elderly people. In the interview, each person was compared with fictitious others who were worse off. After the interviews, the participants completed a life-satisfaction survey and reported more satisfaction with their own lives. Following are hypothetical data similar to those obtained in the research study, representing satisfaction scores for a sample of n = 9 older people who completed the interview. Assume that the average score on the life-satisfaction scale is μ = 20. The scores for the sample are 18, 23, 24, 22, 19, 27, 23, 26, 25.
a. Calculate the mean and standard deviation for the sample.
b. Are the data sufficient to conclude that the people in this sample are significantly more satisfied than others in the general population? Use a one-tailed test with α = .05.
c. Compute Cohen's d to estimate the size of the effect.
d. Compute the 90% confidence interval for the mean life-satisfaction score for people who participate in this type of interview.