1. 2. 3. 4. Assignment for Chapter 8 (Introduction to Hypothesis Testing) Imagine that the average, full-time college senior in the United States spends only μ = 15, σ = 9, hours per week preparing for classes by reading, doing homework, studying, etc. A state university develops a program that is designed to increase student motivation to study. A sample of n = 36 students completes the program and later reports that they spend M = 17 hours per week studying. The university would like to test whether the program resulted in a change in the amount of time spent preparing for class. a. b. C. d. State the null and alternative hypotheses. Compute the standard error of the mean. Compute the z-score statistic. Using a two-tailed hypothesis test with a = .05, what is your decision? (reject the null hypothesis or fail to reject the null hypothesis) Childhood participation in sports, cultural groups, and youth groups appears to be related to improved self-esteem for adolescents. A sample of 49 adolescents with a history of group participation is given a standardized self-esteem questionnaire. For the general population of adolescents, scores on this questionnaire form a normal distribution with a mean of μ = 15 and a standard deviation of σ = 7. The sample of group-participation adolescents had an average of M = 18. a. b. C. Compute the standard error of the mean. Compute the z-score statistic. Using a two-tailed hypothesis test with a = .05, what is your decision? (reject the null hypothesis or fail to reject the null hypothesis) Suppose that a board of directors is interested in evaluating the personality of their leadership. Among a sample of n = 25 managers, the sample mean on the openness to experience dimension of personality was M = 5.0. Assuming that μ = 4.50 with a standard deviation of σ = 1.50, test the hypothesis that this company's business leaders' openness to experience is different from the population. a. b. C. Compute the standard error of the mean. Compute the z-score statistic. Using a two-tailed hypothesis test with a = .05, what is your decision? (reject the null hypothesis or fail to reject the null hypothesis) Some research suggests that screen time and use of social media are related to negative mental health outcomes. In a national survey of adolescents, the mean number of depressive symptoms was μ=2.00 with a standard deviation of σ = 1.20. Suppose that a researcher recruits n = 9 adolescents and instructs them to visit friends or family instead of using social media. The researcher observes that the average number of depressive symptoms is M = 1.40 after the intervention. a. b. Compute the z-score statistic. Using a one-tailed hypothesis test with α = .05, what is your decision? (reject the null hypothesis or fail to reject the null hypothesis) C. Compute Cohen's d to estimate the size of the effect. 5. A researcher is interested in the effect of an educational intervention to improve reading scores for children. The researcher plans to select a sample of children to participate in the educational intervention. After the intervention, the children will take a standardized reading test. The mean scores for the sample will then be compared to the population mean of the test which is u=75 with a standard deviation of σ = 20. State whether the power of the test would increase or decrease based on each of the following: The researcher decides to collect data on a sample of 100 kids instead of 50 kids. Would power increase or decrease? a. b. The researcher decides to test his hypothesis at α = .01 instead of α = .05. Would power increase or decrease? C. The researcher decides to conduct a one-tailed test instead of a two-tailed test. Would power increase or decrease?