Concept explainers
The combination of photochemotherapy with oral methoxsalen (psoralen) and ultraviolet A radiation (called PUVA treatment) is an effective treatment for psoriasis. However, PUVA is mutagenic, increases the risk of squamous-cell skin cancer. and can cause irregular, pigmented skin lesions. Stern et al. [4] performed a study to assess the incidence of melanoma among patients treated with PUVA. The study identified 1380 patients with psoriasis who were first treated with PUVA in 1975 or 1976. Patients were subdivided according to the total number of treatments received (<250 or >250 from 1975 to 1996). Within each group, the observed number of melanomas was determined from 1975 to 1996 and compared with the expected number of melanomas as determined by published U.S. age- and gender-specific melanoma incidence rates. The results were as in Table 7.8.
Interpret the results for Problems 7.69 and 7.70.
Suppose we want to compare the observed and expected number of
Provide a 95% Cl for the expected number of events in the group with > 250 treatments.
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- two types of preoperative skin preparation before performing open heart surgery. These two preparations used aqueous iodine and insoluble iodine. Do these data provide sufficient evidence at the α = 0.05 level to justify the conclusion that they type of skin preparation and infection are associated?arrow_forwardA biochemist is testing the effect of a new antibiotic on a particulararrow_forwardCoronary stenosis (narrowing of the artery supply to the heart muscle) is a direct cause of heart disease. A theory suggests that chronic cytomegalovirus (CMV) infection narrows coronary vessels and leads to coronary heart disease. To test this theory, 75 patients undergoing angioplasty were followed for 6 months following their procedure. The 49 patients who were seropositive for CMV experienced an average luminal diameter reduction of 1.24 mm (s1 = 0.83 mm). In contrast, the 26 patients who were seronegative for CMV experienced an average luminal reduction of 0.68 (s2 = 0.69).k Test whether this mean difference in luminal reduction is significant. Show all hypothesis-testing steps. Do the data support the hypothesis that chronic CMV virus infection plays a role in coronary luminal reduction?arrow_forward
- Captopril is a drug designed to lower systolic blood pressure. When subjects were treated with this drug, their systolic blood pressure readings (in mm Hg) were measured before and after the drug was taken. Results are given in the accompanying table (based on data from "Essential Hypertension: Effect of an Oral Inhibitor of Angiotensin-Converting Enzyme," by MacGregor et al., British Medical Journal, Vol. 2). Using a 0.01 significance level, is there sufficient evidence to support the claim that captopril has an effect on systolic blood pressure?arrow_forwardCoronary stenosis (narrowing of the artery supply to the heart muscle) is a direct cause of heart disease. A theory suggests that chronic cytomegalovirus (CMV) infection narrows coronary vessels and leads to coronary heart disease. To test this theory, 75 patients undergoing angioplasty were followed for 6 months following their procedure. The 49 patients who were seropositive for CMV experienced an average luminal diameter reduction of 1.24mm (s1 = 0.83 mm). In contrast, the 26 patients who were seronegative for CMV experienced and average luminal reduction of 0.68 (s2 = 0.69).k Test whether this mean difference in luminal reduction is significant. Show all hypothesis-testing steps. Do the data support the hypothesis that chronic CMV virus infection plays a role in coronary luminal reduction? What is the 95% confidence interval?arrow_forwardNeutropenia. Neutropenia is an abnormally low number of neutrophils (a type of white blood cell) in the blood. Chemotherapy often reduces the number of neutrophils to a level that makes patients susceptible to fever and infections. G. Bucaneve et al. published a study of such cancer patients in the paper “Levofloxacin to Prevent Bacterial Infection in Patients With Cancer and Neutropenia” (New England Journal of Medicine, Vol. 353, No. 10, pp. 977–987). For the study, 375 patients were randomly assigned to receive a daily dose of levofloxacin, and 363 were given placebo. In the group receiving levofloxacin, fever was present in 243 patients for the duration of neutropenia, whereas fever was experienced by 308 patients in the placebo group. a. At the 1% significance level, do the data provide sufficient evidence to conclude that levofloxacin is effective in reducing the occurrence of fever in such patients? b. Find a 98% confidence level for the difference in the proportions of such…arrow_forward
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- To combat antibiotic resistance a throat swab is recommended to confirm strep throat before a physician prescribes antibiotics to children under age 5. Nationally, 40 percent of children under 5 who received antibiotics did not have a throat swab. The Department of Health took a random sample of 60 children under the age of 5 who received antibiotics for throat infections and found that 18 did not have a throat swab. At α = .05, is this a statistically significant reduction over last year’s national rate of 40 percent?(a) state the null and alternative hypotheses.(b)Calculate the critical valuearrow_forwardThe Dependent variable is the Effectiveness of a new therapeutic technique or Recall on intrusive thougnts? Why?arrow_forwardCadmium, a heavy metal, is toxic to animals. Mushrooms, however, are able to absorb and accumulate cadmium at high concentrations. The Czech and Slovak governments have set a safety limit for cadmium in dry vegetables at 0.5 part per million (ppm). M. Melgar et al. measured the cadmium levels in a random sample of the edible mushroom Boletus pinicola and published the results in the paper “Influence of Some Factors in Toxicity and Accumulation of Cd from Edible Wild Macrofungi in NW Spain” (Journal of Environmental Science and Health, Vol. B33(4), pp. 439–455). A hypothesis test is to be performed to decide whether the mean cadmium level in Boletus pinicola mushrooms is greater than the government’s recommended limit. Hypothesis tests are proposed. For each hypothesis test,a. determine the null hypothesis.b. determine the alternative hypothesis.c. classify the hypothesis test as two tailed, left tailed, or right tailed.arrow_forward
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