Homework 7Confidence Intervals, Effect Size, and Statistical Power
Part I: ConceptsQuestions 1–8
These questions are based on the Nolan and Heinzen reading and end-of-chapter questions.
Part I: Questions 1a-1eFill 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 small 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 ________.
Part I: Questions 2-5End-of-chapter problems: Complete the following problems. If applicable, remember to show work in your homework document to receive partial credit.
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.
A)B)C)D)E)
3) Exercise 8.22 from N&H text: In 2006, approximately 47% of Americans, when surveyed by a Gallup poll, felt that having a gun in the home made them safer than having no gun. The margin of error reported was 3%. 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) 80% (Hint: 10% in each tail): AnswerWork:4b) 88% AnswerWork:
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= .80, d = .09, d = .46, d = .65, d = .28
5a) Calculate the mean effect size of these studies. Answer5b) Use Cohen’s conventions to describe the mean effect size you calculated in part (a). Answer
Part I: Questions 6-8
Compute effect size in the following questions: 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 25 with a standard deviation of 3. 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. AnswerWork:7) On a certain anxiety questionnaire, the general population is known to have a mean of 16 and a standard deviation of 2.4. 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 12.5.What is the effect size of the relaxation program?AnswerWork:
8) 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 15 and a standard deviation of 1.6. The mean score for the patients after the new group therapy is 13.7. What is the effect size of the new group therapy?AnswerWork:
Part II & Part IIIThere 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 40 39 50 32 47 65 43 59
56 39 63 45 46 54 35 61 56 52
Part IV:
Questions 1-4A 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. (higher scores à 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 graphJustification
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 45th percentile of this data set. (See last week’s material for review.)AnswerWork: 4) Using the mean and standard deviation of the helping behaviors data above, calculate the percentile of a raw score of 37. (See last week’s material for review.)AnswerWork
Part IV:Question 5a-5e
For the following scores, state the: a) mean; b) median; c) mode; d) range; e) standard deviation.39 35 43 27 355-a) MeanAnswerWork:
5-b) MedianAnswerWork:
5-c) ModeAnswerWork:
5-d) RangeAnswerWork:
5-e)Standard Deviation (Note: Compute by hand using the formula from Module 3. Programs like SPSS or Excel use a slightly different formula that we won’t use until Module 8 and will give you the wrong answer for this section.)AnswerWork:
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