PSYC 354 HOMEWORK 7 Confidence Intervals, Effect Size, and Statistical Power When submitting this file, be sure the filename includes your full name, course and section. Example: HW7_JohnDoe_354B01 Be sure you have reviewed this module/week's lesson and presentations along with the practice data analysis before proceeding to the homework exercises. Complete all analyses in SPSS, then copy and paste your output and graphs into your homework document file. Answer any written questions (such as the text-based questions or the APA Participants section) in the appropriate place within the same file. Part I: Concepts Questions 1-8: Answer the questions in the spaces provided. Part I: Questions 1a-1e Fill in the highlighted blanks with the best word or words. 1-a) The confidence interval is centered around the _____ of the sample. 1-b) Cohen's d measures the difference between means in terms of ____. 1-c) According to Cohen's conventions, a d value of _____ indicates a large effect. 1-d) A study that calculates the mean effect size from the individual effect sizes of many studies is called a(n) ____. 1-e) Statistical power refers to the probability of successfully rejecting the ____ hypothesis. Part I: Questions 2-5 End-of-chapter problems: Complete the following problems. If applicable, remember to show work in your homework document to receive partial credit. Page 1 of 5 PSYC 354 2) List five factors that affect statistical power. For each, indicate how a researcher can leverage/manipulate that factor to increase power in a study. Increase statistical power by: 1. 2. 3. 4. 5. 3) In a public opinion poll, approximately 89% of Americans felt that having a police officer on patrol in the neighborhood made them safer than having no police officer on patrol. The margin of error reported was 5%. Construct an interval estimate using these figures. Answer 4) For each of the following confidence levels, look up the critical z-values for a two-tailed test. 4a) 90% (Hint: 10% in each tail): Work: 4b) 95% Work: 5) Remembering that a meta-analysis calculates one mean effect size using the effect sizes of several studies, assume you are conducting a meta-analysis over a set of five studies. The effect sizes for each study are: d= .78, d = .12, d = .50, d = .13, d = .37 5a) Calculate the mean effect size of these studies. 5b) Use Cohen's conventions to describe the mean effect size you calculated in part (a). Part I: Questions 6-8 Compute effect size in the following questions: Page 2 of 5 PSYC 354 6 ) 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 personnel at this national company is 26 with a standard deviation of 4.5. The mean number of sales per month for those who participated in the new program is 30. Compute the effect size of the new sales program. Answer 7 ) On a certain anxiety questionnaire, the general population is known to have a mean of 19 and a standard deviation of 2.1. 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 16.5. What is the effect size of the relaxation program? Answer 8 ) Work: Work: A residential treatment facility tests a new group therapy for patients with selfdestructive behaviors. The therapists hope to decrease scores on a measure of selfdestructive behaviors that has a mean in the overall residential treatment population of 17 and a standard deviation of 1.8. The mean score for the patients after the new group therapy is 15.2. What is the effect size of the new group therapy? Answer Work: Part II & Part III There is no new SPSS material this module/week. No questions for Part II or III Part IV: Cumulative Data provided below for respective questions. Helping Behaviors 47 52 49 40 30 61 40 42 48 46 37 53 46 34 60 63 41 52 59 51 Part IV: Questions 1-4 A test designed to measure helping behavior was administered to 20 university students. The data from this test are shown in the column to the left. Page 3 of 5 PSYC 354 (higher scores more helping) Enter the Helping Behaviors data into a new SPSS file. 1-a) Using SPSS, calculate descriptive statistics for this variable. Be sure to include the mean and standard deviation. Answer: Descriptive Statistics Table 2) Create the appropriate graph in SPSS for the variable \"Helping Behaviors.\" Justify your choice of graph. Answer: Appropriate graph Justification 3) Using the mean and standard deviation of the helping behaviors data above (from your SPSS output), calculate (by hand) the raw score that marks the 40th percentile of this data set. (See last module/week's material for review.) Answer Work: 4) Using the mean and standard deviation of the helping behaviors data above, calculate the percentile of a raw score of 46. (See last module/week's material for review.) Answer Work: Page 4 of 5 PSYC 354 Part IV: Questions 5a-5e For the following scores, state the: a) mean; b) median; c) mode; d) range; e) standard deviation. 12 19 25 15 21 5-a) Mean Answer Work: 5-b) Median Answer 5-c) Work: Mode Answer Work: 5-d) Range Answer 5-e) Work: Standard Deviation (Note: Compute by hand using the formula from Module/Week 3. Programs like SPSS or Excel use a slightly different formula that you will not use until Module/Week 8 and will give you the wrong answer for this section.) Answer Work: Submit Homework 7 by 11:59 p.m. (ET) on Monday of Module/Week 7. Remember to name file appropriately. Done! Page 5 of 5