Some researchers claim that childhood participation in organized sports is related to improved self-esteem for adolescents. To test this claim, a researcher selects a sample of n = 20 adolescents with a history of participation on a sports team. Each adolescent is given a standardized self-esteem questionnaire. For the general population of adolescents, scores on the questionnaire are normally distributed with = 75 and = 15. The sample of n = 20 adolescents with a history of participation had a mean score of M = 85.

Can the researcher conclude that scores on the self-esteem questionnaire for this sample of adolescents are significantly different from those of the general population? Use a two-tailed test with = .05. Be sure to state your null hypothesis, a decision about that null hypothesis, and a conclusion explaining your results written in a paragraph. Calculate Cohen's d if necessary. Make sure you show your math and explain why