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PSYC 354

Homework 6

Effect Size Assignment

Answer each question about effect size. Remember to show your work. Submit your assignment to Blackboard as a Word document. (35 pts possible)

1. A company decides to add a new program that prepares randomly selected sales personnel to increase their number of sales per month. The mean number of sales per month for the overall population of sales people at this national company is 25 with a standard deviation of 4. The mean number of sales per month for those who participated in the new program was 29. Compute the effect size of the new sales program. (5 pts)

2. On a certain anxiety questionnaire, the population is known to have a mean of 12 and a standard deviation of 2.3. A higher score represents higher levels of anxiety. Participants in a new relaxation program complete the questionnaire after completing the program, and have a mean score of 10.2. What is the effect size of the relaxation program? (5 pts)

3. A private tutoring company has made the claim that its tutoring package will improve GRE Verbal test scores by at least 25 points. A graduate student in psychology hears this claim and decides to test their theory. After gathering 10 undergraduate students who are willing to participate in the program, he wants to predict the effect size for an increase of 25 points, assuming a GRE Verbal test mean in the population of 462 and a standard deviation of 119. What is the predicted effect size for a projected increase of 25 points? (5 pts)

4. A school psychologist is planning to study the effect of a new anger management program on the aggressive behavior of students at her high school. She knows that the mean number of aggressive behaviors at her school is 14 per week, with a standard deviation of 3.2, but she would like to cut this number in half to 7 events per week as a first benchmark goal of the anger management program. What is the predicted effect size for this projected decrease in aggressive behaviors? (5 pts)

5. A residential treatment facility tests a new group therapy for patients with self-destructive behaviors. The therapists hope to decrease scores on a measure of self-destructive behaviors that has a mean in the overall residential treatment population of 35 and a standard deviation of 4.7. The mean score for the patients after the new group therapy is 27. What is the effect size of the new group therapy? (5 pts)

6. Use Cohen’s conventions for effect sizes to label the following as small, medium, or large effects: (1 pt each for a-e)

a. .15

b. -.81

c. -.59

d. .32

e. .67

7. Using a diagnostic interview, a counselor notes a significant decrease in symptoms in patients who have been treated for depression. He computes the effect size based on his data, and finds that d = -.67. Based on Cohen’s conventions, what size is this effect? (5 pts)

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