The article “The Effects of a Low-Fat, Plant-Based Dietary Intervention on Body Weight, Metabolism, and Insulin Sensitivity in Postmenopausal Women” (Amer. J. of Med., 2005: 991–997) reported on the results of an experiment in which half of the individuals in a group of 64 postmenopausal overweight women were randomly assigned to a particular vegan diet, and the other half received a diet based on National Cholesterol Education Program guidelines. The sample mean decrease in body weight for those on the vegan diet was 5.8 kg, and the sample SD was 3.2, whereas for those on the control diet, the sample mean weight loss and standard deviation were 3.8 and 2.8, respectively. Does it appear the true average weight loss for the vegan diet exceeds that for the control diet by more than 1 kg? Carry out an appropriate test of hypotheses at significance level .05.
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- The article “The Effects of a Low-Fat, Plant-Based DietaryIntervention on Body Weight, Metabolism, and InsulinSensitivity in Postmenopausal Women” (Amer. J. of Med.,2005: 991–997) reported on the results of an experiment inwhich half of the individuals in a group of 64 postmenopausaloverweight women were randomly assigned to a particularvegan diet, and the other half received a diet based on NationalCholesterol Education Program guidelines. The sample meandecrease in body weight for those on the vegan diet was 5.8kg, and the sample SD was 3.2, whereas for those on the control diet, the sample mean weight loss and standard deviationwere 3.8 and 2.8, respectively. Does it appear the true averageweight loss for the vegan diet exceeds that for the control dietby more than 1 kg? Carry out an appropriate test of hypotheses at significance level .05 based on calculating a P-valuearrow_forwardAspirin and Cardiovascular Disease. In the article by P. Ridker et al. titled “A Randomized Trial of Low-dose Aspirin in the Primary Prevention of Cardiovascular Disease inWomen” (New England Journal of Medicine, Vol. 352, pp. 1293–1304), the researchers noted that “We randomly assigned 39,876 initially healthy women 45 years of age or older to receive 100 mg of aspirin or placebo on alternate days and then monitored them for 10 years for a first major cardiovascular event (i.e., nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes).”arrow_forward) Name one other limitation in this study (do not repeat any of the limitations you may have named above in your previous answers) and suggest how you would improve it.arrow_forward
- Popular Diets. In the article “Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction” (Journal of the American Medical Association, Vol. 293, No. 1, pp. 43–53), M. Dansinger et al. conducted a randomized trial to assess the effectiveness of four popular diets for weight loss. Overweight adults with average body mass index of 35 and ages 22–72 years participated in the randomized trial for 1 year. The weight losses, in kilograms, based on the results of the experiment are given on the WeissStats site. Negative losses are gains. WW = Weight Watchers. a. Obtain individual normal probability plots and the standard deviations of the samples. b. Perform a residual analysis. c. Use your results from parts (a) and (b) to decide whether conducting a one-way ANOVA test on the data is reasonable. If so, also do parts (d) and (e). d. Use a one-way ANOVA test to decide, at the 5% significance level, whether the data provide sufficient…arrow_forwardAngioplasty is a medical procedure in which an obstructed blood vessel is widened. In some cases, a wire mesh tube, called a stent, is placed in the vessel to help it remain open. The article “Long-term Outcomes of Patients Receiving Drug-eluting Stents” (A. Philpott, D. Southern, et al., Canadian Medical Association Journal, 2009:167–174) presents the results of a study comparing the effectiveness of a bare metal stent with one that that has been coated with a drug designed to prevent reblocking of the vessel. A total of 5320 patients received bare metal stents, and of these, 841 needed treatment for reblocking within a year. A total of 1120 received drug coated stents, and 134 of them required treatment within a year. a) Find a 98% confidence interval for the differences between the proportions for drug coated stents and bare metal stents. b) Suppose that additional patients are to be treated in order to increase the precision of the confidence interval. Three sampling plans are…arrow_forwardResearchers recruited 1000 10- and 20-year-olds to participate in a study about age differences in aggression and the impact of violent video games on aggression. For 1-hour per day, half the participants were randomly assigned to play violent video games, while the other half played a nonviolent video game. A test for aggression was administered at the end of the year, and each participant received a score between 1 and 50 (higher scores indicate greater aggression). The results of the study are shown below: Factor 1 10 years 20 years old old Violent 35 25 Factor games 2 Nonviolent 25 45 games Is there a main effect of age? If so, which age shows more aggression?arrow_forward
- Sleep apnea is a disorder in which there are pauses in breathing during sleep. People with this condition must wake up frequently to breathe. The article “Postoperative Complications in Patients With Obstructive Sleep Apnea Syndrome Undergoing Hip or Knee Replacement: A Case-Control Study” (R. Gupta, J. Parvizi, et al., Mayo Clinic Proceedings, 2001:897–905) reported that in a sample of 427 people 65 and over, 104 of them had sleep apnea. a) Find a 95% confidence interval for the proportion of those 65 and over who have sleep apnea. b) Find a 99% confidence interval for the proportion of those 65 and over who have sleep apnea. c) Find the sample size needed for a 95% confidence interval to specify the proportion to within ±0.03. d) Find the sample size needed for a 99% confidence interval to specify the proportion to within ±0.03.arrow_forwardDo cell phones increase drivers' reaction times while driving? A 2003 American Journal of Health Education study investigated the effects of cell phone use on reaction time. In the study, 60 participants were randomly selected and placed into one of two groups: the cell phone group or the control group. Those in the control group participated in the experiment with no distractions, whereas those in the cell phone group had access to text documents on a cell phone. Participants in each group were then asked to take a computerized reaction time test. Researchers then recorded each subject's reaction time in seconds. The table shows the results of the experiment. Group Populationmean Samplesize Samplemean Sample standarddeviation Phone up n=30 x¯P=0.546 sx=0.213 Control uc n=30 x¯C=0.356 sx=0.245 df=56.900 Suppose the researchers wish to examine at a significance level of alpha=0.05 if the mean reaction time for phone users is larger than the mean reaction time for the…arrow_forwardVasectomies and Prostate Cancer. In the United States, approximately 450,000 vasectomies are performed each year. In this surgical procedure for contraception, the tube carrying sperm from the testicles is cut and tied. Several studies have been conducted to analyze the relationship between vasectomies and prostate cancer. The results of one such study by E. Giovannucci et al. appeared in the paper “A Retrospective Cohort Study of Vasectomy and Prostate Cancer in U.S. Men” (Journal of the American Medical Association, Vol. 269(7), pp. 878–882). Of 21,300 men who had not had a vasectomy, 69 were found to have prostate cancer; of 22,000 men who had had a vasectomy, 113 were found to have prostate cancer. a. At the 1% significance level, do the data provide sufficient evidence to conclude that men who have had a vasectomy are at greater risk of having prostate cancer? Consider men who had had a vasectomy Population 2. b. Is this study a designed experiment or an observational study?…arrow_forward
- Q1: Placebo effect of exercise In a high-profile research study, Crum and Langer (2007) performed an experiment to test whether the relationship between physical exercise and health is impacted by one's mindset: in other words, if there is any "placebo effect" of exercise. A sample of 84 randomly selected hotel workers in the United States were placed either into a treatment group (n=44) or control group (n=40) depending on which hotel they worked at. The treatment group was given information demonstrating how their work is good physical exercise, while the control group was not given this information. They measured the body mass index (BMI) for each worker before the experiment and again four weeks after the experiment. a. Are the treatment group and control group independent of each other, and if so why? b. Now consider the treatment group alone: are the measurements of BMI taken before and after the experiment independent of each other, and if so why? c. What is the most appropriate…arrow_forwardusing SASarrow_forwardAn article from the American Journal of Public Health reports the results from a randomized study designed to evaluate the efficacy of an intervention targeted to Hispanic/Latino men who identify as gay, bi-sexual or other men who have sex with men (MSM). A representative sample of 254 such men was randomized to be in either the intervention group (n=152, with 141 ultimately participating in the study) or the control group (n=152, with 147 ulitmately participating in the study). The primary outcome under study getting tested for HIV within the six-months following group assignment (randomization) among those who had been sexually active in this same six-month follow-up period. At six months of follow-up, 141 subjects in the intervention group reported having had sex (with men and/or women) since randomization. Of these 141 men, 114 had been tested for HIV since being randomized. At six months of follow-up, 147 subjects in the control group reported having had sex (with men…arrow_forward
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