Directions: Answer each of the following questions on a separate sheet of paper. Please show ALL work for computations. 1. A researcher hypothesizes that daily exercise decreases stress level in adults. On a national survey, the mean stress level () for adults who do not exercise is 54.25. The researcher randomly selects a sample of 19 adults and assigns them to exercise daily for 2 weeks. After 2 weeks of exercise, the mean stress level for this sample was 49.70, s2x = 64. a. b. c. d. e. f. g. State H0 and Ha. What is the critical value of t (tcrit) when =.05? Compute t and write out your answer using the format discussed in class. What is your decision (i.e., do you reject or retain H0)? State your conclusion in the context of this research question. Compute the 95% CI. Interpret the 95% CI. 2. A researcher hypothesizes that a person's style of dress affects how persuasive he is. She recruited 31 adult volunteers and randomly assigned 16 to watch a videotape of someone dressed in a business suit giving a 5-minute speech on the importance of saving for retirement (Video A) and the other 15 to watch a video of the same person give the same speech while dressed in jeans and a t-shirt (Video B). After viewing the video, each participant rated how likely he/she was to start retirement savings using a scale of 1 (not at all) to 50 (certain). The mean score for participants who watched Video A was 37.1 (s2x = 5.7). The mean score for participants who watched Video B was 35.6 (s2x = 5.1). a. b. c. d. e. State H0 and Ha. What is the critical value of t (tcrit) when =.05? Compute tobt and write out your answer using the format discussed in class. What is your decision (i.e., do you reject or retain H0)? State your conclusion in the context of this research question. 3. A researcher investigates whether supplementing the diet with extra amounts of Vitamin A improves ability to see under dim lighting conditions. She recruits volunteers and randomly assigns 12 to receive Vitamin A supplements and 12 to eat a normal diet (without Vitamin A supplements). After 1 week on this program, all participants take a vision test under dim lighting conditions and their scores are recorded. The mean score for participants who received Vitamin A supplements was 24.6 (s2x = 2.1). The mean score for participants who did not receive Vitamin A supplements was 22.9 (s2x = 2.0). a. b. c. d. e. f. g. State H0 and Ha. What is the critical value of t (tcrit) when =.05? Compute tobt and write out your answer using the format discussed in class. What is your decision (i.e., do you reject or retain H0)? State your conclusion in the context of this research question. If appropriate, compute the 95% CI. If appropriate to compute the 95% CI, interpret it in the context of this research example. SEE NEXT PAGE FOR EXTRA CREDIT QUESTIONS EXTRA CREDIT (optional; 5 points) 1. (1 point) To determine whether a new medication is effective in lowering a person's heart rate, Dr. Smith administers this medication to a random sample of 100 patients with rapid heart rhythm and computes the mean heart rate. He knows that in the population, the mean heart rate for individuals with rapid heart rhythm is 135, x=40. Which parametric test should be used in this example to determine whether the new medication is effective? (You do not need to compute the statistic; just identify the appropriate test). 2. (1 point) You are interested in the effect of age on detail recall. You select a random sample of 20 12-year olds from the local middle school and a random sample of 20 16-year olds from the local high school. You administer a test paragraph, record how many details each participant can remember, and compute the sample means. Which parametric test should be used in this example to determine whether age affects recall? (You do not need to compute the statistic; just identify the appropriate test). 3. an experiment? (3 points) What are 3 things a researcher can do to increase power in