Ohio State University researchers conducted a meta-analysis of 53 studies totaling almost 8500 participants (Lull & Bushman, 2015). Their goal was to determine whether advertising that included sex or violence helped to sell products. The researchers reported that “memory for brands and ads was significantly impaired in programs containing sex, violence, or both sex and violence, d = - 0.39; 95%Cl = - 0.55, - 0.22” (p. 1029). (They found similar results for participants’ reported intention to buy products associated with sex or violence.)

a. What is the confidence interval for the effect size?

b. Based on the confidence interval, would a hypothesis test lead us to reject the null hypothesis that the effect size is zero? Explain.

c. Why would a graph, such as a forest plot, be useful when conducting a meta-analysis like this one? (Hint: Consider the problem when using a mean as the measure of central tendency.)