19. In the Decision Errors, Effect Size, and Power in Research Articles section earlier in this chapter, you read about a review study conducted by Huey and Polo

(2008) that examined psychological treatments for clinical problems among ethnic minority youth. As part of their review, the researchers identified twentyfive studies that compared the effect of a psychotherapy treatment versus a control treatment on youths’ clinical problems. They conducted a meta-analysis of the twenty-five studies and reported the results as follows:

Explain the purpose and results of this meta-analysis to someone who is familiar with effect size but has never heard of meta-analysis.