It appears that there is some truth to the old adage

“That which doesn’t kill us makes us stronger.” Seery, Holman, and Silver (2010) found that individuals with some history of adversity report better mental health and higher well-being compared to people with little or no history of adversity. In an attempt to examine this phenomenon, a researcher surveys a group of college students to determine the negative life events that they experienced in the past 5 years and their current feeling of well-being. For n 5 7 participants with 2 or fewer negative experiences, the average well-being score is M 5 41 with s 2 5 50, and for n 5 7 participants with 5 to 10 negative experiences the average score is M 5 48 with s 2 5 62.

a. Use an independent-measures t hypothesis test with a 5 .05 to determine whether there is a significant difference between the two populations represented by these two samples and calculate Cohen’s d to measure effect size for the mean difference.

b. Now assume that each sample has n 5 15 participants and repeat the hypothesis test and calculation of Cohen’s d.

c. Comparing your answers for Parts a and

b, describe how sample size influences the outcome of the hypothesis test and the measure of effect size.