A case-control (or retrospective) study was conducted to investigate a relationship between the colors of helmets worn by motorcycle drivers and whether they are injured or killed in a crash. Results are given in the accom significance level, test the claim that injuries are independent of helmet color. Color of Helmet White Yellow 331 32 Red Black 482 Blue Controls (not injured) 159 100 Cases (injured or 211 109 8 65 47 killed) Click here to view the chi-square distribution table
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- An article23 summarized results from the Nurses’ Health Study and the Health Pro- fessionals Follow-Up Study. The article reported (with RR = relative risk) that “Com- pared with nonregular use, regular aspirin use was associated with lower risk of overall cancer (RR 0.97; 95% CI 0.94, 0.99), which was primarily due to a lower incidence of gastrointestinal cancers, especially colorectal cancers (RR 0.81; 95% CI 0.75, 0.88).” Identify the response variables and the explanatory variable for these two results. Explain how to interpret the confidence interval about colorectal cancers. Would the association with overall cancer be considered (i) significant or non- significant? (ii) strong or weak? Explain. question 1 and 2A case–control study of patients on antihypertensive drugs related an increased risk of myocardial infarction (MI) for patients using calcium channel blockers (Psaty, et al.,1995). In this study, cases were antihypertensive drug patients who had suffered a first fatal or nonfatal MI through 1993, and controls were antihypertensive patients, matched by demographic factors, who had not suffered a MI. Among the comparisons reported were patients receiving calcium channel (CC) blockers (with and without diuretics) and patients receiving β–blockers (with and without diuretics). Results of numbers of patient by drug/MI status combination are given in Table 1. Compute the odds ratio of suffering MI (CC blockers relative to β–blockers), and the corresponding 95% CI. Does it appear that calcium channel blockers are associated with higher odds (and thus probability) of suffering MI than β –blockers? Table 1: Observed cell counts for antihypertensive drug/MI data Occurrence of…Rogers, Farlow, and colleagues (1998) conducted an experiment to investigate whether donepezil improved cognitive function in patients with mild to moderate Alzheimer’s disease (AD). A total of 1,775 patients were randomly assigned to treatment with either donepezil or a placebo (a look-alike pill with no pharmacological effect). Cognitive function, as measured by the Alzheimer’s Disease Assessment Scale (ADAS-cog), was significantly improved in patients taking donepezil compared with the placebo group at weeks 12, 18, and 24. [Source: Rogers, S. L., Farlow, M. R., Doody, R. S., et al. (1998). A 24-week, double-blind, placebo controlled trial of donepezil in patients with Alzheimer’s disease. Neurology, 50, 136–145.] In this experiment, the independent variable is , and the dependent variable is . The individuals who are in the control condition are typically referred to as the control group. Here, the control group consists of . is a construct that is being tested in this…
- A fast-food chain decided to carry out an experiment to assess the influence of advertising expenditure on sales. Different relative changes in advertising expenditure, compared to the previous year, were made in eight regions of the country, and resulting changes in sales levels were observed the accompanying table shows the results. Increase in advertising expenditure (%) 0 5 15 20 25 30 35 40 Increase in sales (%) 5 10 18 25 35 50 60 65 A fast-food chain decided to carry out an experiment to assess the influence of advertising expenditure on sales. Different relative changes in advertising expenditure, compared to the previous year, were made in eight regions of the country, and resulting changes in sales levels were observed the accompanying table shows the results. Increase in advertising expenditure (%) 0 5 15 20 25 30 35 40 Increase in sales (%) 5 10 18 25 35 50 60 65 d-Test the…Aortic stenosis refers to a narrowing of the aortic valvein the heart. The article “Correlation Analysis ofStenotic Aortic Valve Flow Patterns Using PhaseContrast MRI” (Annals of Biomed. Engr., 2005:878–887) gave the following data on aortic root diameter(cm) and gender for a sample of patients having variousdegrees of aortic stenosis:M: 3.7 3.4 3.7 4.0 3.9 3.8 3.4 3.6 3.1 4.0 3.4 3.8 3.5F: 3.8 2.6 3.2 3.0 4.3 3.5 3.1 3.1 3.2 3.0a. Compare and contrast the diameter observations forthe two genders.b. Calculate a 10% trimmed mean for each of the twosamples, and compare to other measures of center(for the male sample, the interpolation method mentionedin Section 1.3 must be used).A mail-order catalog firm would like to test the effect of the size of a magazine advertisement and the advertisement design on the number of catalog requests received (data in thousands). Three advertising designs and two different size advertisements were considered. The data obtained follow. At the 0.05 level of significance, a. Is there an interaction between type of design and size of advertisement? b. Is there an effect due to type of design? c. Is there an effect due to size of advertisement?
- In a study reported in the American Journal of Clinical Nutrition, young men who drank fat-free milk after exercising gained 40% more muscle mass than those who drank a soy beverage after exercising. Fat-free milk drinkers gained 60% more muscle mass than those who consumed a sweetened sports drink. What is the response variable in this study? What is the explanatory variable in this study? What is the role – type classification of the variables in this study?Does St. John wort (an herb) have a siginifact effect in treating major depression? A study looked at 340 adult outpatients suffering as measured by their HAM-Dscore, randomly assiging each subject to either a placebo, St.John's wort, or a second active treatment for comparison. The study found the diiference in treating major depression as measured by improvement in HAM-D scores between St.John's wort and the placebo was not statistically significant This means that: A. a difference this big could easily occur just by chance even if St. John's wort does not better than the placebo B. We cannot make a 95 percent confidence statement C.The placebo makes no difference in the subjects' depression D. The study was badly designedMcAllister et al. (2012) compared varsity football and hockey players with varsity athletes from noncontact sports to determine whether exposure to head impacts during one season have an effect on cognitive performance. In the study, tests of new learning performance were significantly poorer for the contact sport athletes compared to the noncontact sport athletes. The following table presents data similar to the results obtained in the study. Noncontact Athletes: 10, 8, 7, 9, 13, 7, 6, 12 Contact Athletes: 7, 4, 9, 3, 7, 6, 10, 2 a. Are the test scores significantly lower for the contact sport athletes than for the noncontact athletes? Use a two-tailed test with =.05 b. What sampling technique was most likely employed by the researcher? justify your answer c. Does exposure to head impacts have an effect on cognitive performance? why or why not
- McAllister et al. (2012) compared varsity football and hockey players with varsity athletes from noncontact sports to determine whether exposure to head impacts during one season have an effect on cognitive performance. In the study, tests of new learning performance were significantly poorer for the contact sport athletes compared to the noncontact sport athletes. The following table presents data similar to the results obtained in the study. Noncontact Athletes: 10, 8, 7, 9, 13, 7, 6, 12 Contact Athletes: 7, 4, 9, 3, 7, 6, 10, 2 a. Are the test scores significantly lower for the contact sport athletes than for the noncontact athletes? Use a one-tailed test with =.05 t-critical= t= b. Compute the value of (percentage of variance accounted for) for these data. r^2= a. 0.123, b. 0.239, c. 0.138, d. 0.264An investigation was carried out to study possible consequences of the high incidence of head injuries among soccer players. Three groups of college students (soccer athletes, nonsoccer athletes, and a control group consisting of students who did not participate in intercollegiate sports) were considered in the study. The following table gives information on scores from the Hopkins Verbal Learning Test (which measures immediate memory recall). In addition = 30.1809. SoccerAthletes NonsoccerAthletes Control Sample size 85 94 54 Sample mean score 30.90 30.14 29.12 Sample standarddeviation 3.53 5.34 3.58 Suppose that it is reasonable to regard these three samples as random samples from the three student populations of interest. Is there sufficient evidence to conclude that the means for Hopkins score are not the same for the three student populations? Use ? = 0.05. (Round your answer to two decimal places.) F = Use technology to find the P-value. (Round your answer to…A Canadian study measuring depression level in teens (as reported in the Journal of Adolescence, vol. 25, 2002) randomly sampled 112 male teens and 101 female teens, and scored them on a common depression scale (higher score representing more depression). The researchers suspected that the mean depression score for male teens is higher than for female teens, and wanted to check whether data would support this hypothesis. What conclusion can you draw from the output? The data provide sufficient evidence to reject H0 and to conclude that the mean depression score for male teens is larger than that of female teens. The data provide sufficient evidence to conclude that male and female teens do not differ in mean depression score. The data do not provide sufficient evidence to conclude that the mean depression score of male teens is larger than that of female teens. The data do not provide sufficient evidence to reject H0, so we accept it, and conclude that male and female teens do…