A study examines self-esteem and depression in children

 A study examines self-esteem and depression in children. A sample of 25 children with low self- esteem is given a standardized test for depression. The average score for the group is M = 93.3. For the general population, scores on the depression test form a normal distribution with a mean of Mu = 90 and a standard deviation of = 15. Do children with low self-esteem show significantly more depression? Use a one- tailed test with alpha =.05.

b. An educational psychologist studies the effect of frequent testing on retention of course material. In one of the professor's sections, students are given quizzes each week. The second section receives only two tests during the semester. At the end of the semester, both sections receive the same final exam, and the scores are summarized below.

1. Does the data indicate that testing frequency had a significant effect of performance? Use a two-tailed test at the .01 level of significance.
2. Compute r squared, the percentage of variance that is explained by the treatment difference.

Frequent Quizzes Two exams
n=15 n=15
M=72 M=68
SS=100 SS=110