Which of the following statements is correct?
a. The predictive value of a positive result is 31/343
b. The predictive value of a positive result is 79/312
c. The predictive value of a negative result is 578/(578 + 31)
d. The predictive value of a negative test is 578/657
e. The incidence rate of cholera in this population is 343/1000
19. The RAC test achieves widespread acceptance. However, with improvements in hygiene, the prevalence of cholera gradually falls from 35 to 5% of hospitalized diarrhea patients. Which statement about the effect of this fall in prevalence is true?
a. The change in prevalence will reduce the predictive value of a negative result b. The predictive value of a positive result will decline c. The specificity of the test is likely to decline d. The specificity of the test will increase at the expense of its sensitivity e. It will have no impact on the predictive values of the test
20. A randomized clinical trial is undertaken to examine the effect of a new combination of antiretroviral drugs on HIV viral load compared to usual therapy. Randomization is used for allocation of subjects to either treatment or control (usual care) groups in experimental studies. Randomization ensures that a. Assignment occurs by chance b. Treatment and control (usual care) groups are alike in all respects except treatment c. Bias in observations is eliminated d. Placebo effects are eliminated e. An equal number of persons will be followed in the treatment and control group
21. In a study of the cause of lung cancer, patients who had the disease were matched with controls by age, sex, place of residence, and social class. The frequency of cigarette smoking was then compared in the two groups. What type of study was this?
a. Prospective cohort b. Retrospective cohort c. Clinical trial d. Case-control e. Correlation
22. What is the relative risk of developing lung cancer for smokers compared with nonsmokers?
23. What percentage of lung cancer can be attributed to smoking?
24. If the prevalence of smoking in the community was decreased to 10%, the excess incidence rate of lung cancer that could be averted in that community would be a. 11/100,000
25. The Coronary Drug Project was a randomized trial to evaluate the efficacy of several lipid-lowering drugs. The five-year mortality of the men who adhered to the regimen of clofibrate (i.e., took 80% of their medicine or more) was 15%; among those assigned to the clofibrate group who were less compliant, it was 24.6%. The result was highly statistically significant (p < 0.0001). From this one can conclude a. Clofibrate was very beneficial to the patients who took it reliably b. Clofibrate is not effective unless patients take at least 80% of the recommended doses c. Either clofibrate or something associated with taking it reliably is strongly associated with reduced total mortality d. There was a problem with blinding in this study e. Only those who were compliant should be included in the data
26. The use of matching as a technique to control for confounding is most appropriate for which type of study?
a. A large-scale cohort study b. A case-control study with a small number of cases c. A clinical trial with a factorial design d. A cross-sectional study with multiple variables e. A correlation study with a small number of countries
An investigator is designing a randomized, double-blind, placebo-controlled clinical trial to see whether vitamin E will prevent lung cancer.
27. Which technique is likely to maximize compliance with the allocated regimen?
a. Using the placebo b. Performing a run-in phase c. Using intent-to-treat analysis d. Double blinding the study e. Limiting the number of subjects enrolled
28. Which is most likely to affect the validity (source of bias) of the study?
a. Loss to follow-up b. Incidence of lung cancer c. Prevalence of smoking in the source population d. a error e. P error
29. The crude death rate in the United States is 150/100,000. The crude death rate in a smaller, developing country is 75/100,000. Based on these data, which one of the following statements best explains the data?
a. The health care system of the developing country is far better than that in the United States b. More people die in the United States because it has a larger population c. Infant mortality in the first week is higher in developing countries, but it is not included in the crude death rate d. Death rates in the developing country are lower due to the emigration effect e. Crude death rates are usually higher in developed countries because of a higher proportion of older persons in the population
A research team wishes to investigate a possible association between smokeless tobacco and oral lesions among professional baseball players. At spring training camp, they ask each baseball player about current and past use of smokeless tobacco, cigarettes, and alcohol, and a dentist notes the type and extent of the lesions in the mouth.
30. What type of study is this?
a. Case-control b. Cross-sectional c. Prospective cohort d. Clinical trial e. Retrospective cohort
31. After the players have been questioned about use of smokeless tobacco and examined for lesions of the mouth, the data on the 146 players are tabulated as follows:
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