HLTH 503 Final Exam Questions with Complete Solutions (Already Passed

HLTH 503 Final Exam Questions with Complete Solutions (Already Passed) True or False? Reliability refers to the ability of a measuring instrument to give consistent results on repeated trials, regardless of its accuracy. - Answers True A new screening test for Lyme disease is developed for use in the general population. The sensitivity and specificity of the new test are 60% and 70%, respectively. Three hundred people are screened at a clinic during the first year the new test is implemented. Assume the true prevalence of Lyme disease among clinic attendees is 10%. Calculate the following value The predictive value of a positive test is: - Answers 18.2% True or False? Sensitivity refers to the ability of a screening test to correctly identify all screened individuals who have a disease. - Answers True A new antibody test detects serum antibodies against virus X (sensitivity 99%, specificity 90%). When applied in a group of hospitalized patients diagnosed as having virus X infections, the test is found to have a positive predictive value of 85%. When used to screen a group of healthy blood donors for virus X infections, the test is found to have a positive predictive value of 30%. Which of the following best explains this difference between the positive predictive values? - Answers The prevalence of virus X infection is higher among the hospital patients than among blood donors True or False? Specificity refers to the ability of a screening test to identify only nondiseased individuals who actually do not have the disease. - Answers True A new screening test for Lyme disease is developed for use in the general population. The sensitivity and specificity of the new test are 60% and 70%, respectively. Three hundred people are screened at a clinic during the first year the new test is implemented. Assume the true prevalence of Lyme disease among clinic attendees is 10%. Calculate the following value The number of false positives is: - Answers 81 The degree of agreement among several trained experts refers to: - Answers inter-judge reliability A screening examination was performed on 250 persons for Factor X, which is found in disease Y. A definitive diagnosis for disease Y among the 250 persons had been obtained previously. The results are charted below: The sensitivity of this test is expressed as: - Answers 80% Sensitivity and specificity of a screening test refer to its: - Answers Validity True or False? Validity is the ability of a measuring instrument to give a true measure. - Answers True A test that determines whether disease is actually present is a: - Answers diagnostic test A screening examination was performed on 250 persons for Factor X, which is found in disease Y. A definitive diagnosis for disease Y among the 250 persons had been obtained previously. The results are charted below: The specificity of this test is expressed as: - Answers 70% True or False? Incubation period refers to the time between the start of an infection and the beginning of the period of communicability. - Answers False True or False? Herd immunity must be 100% to confer protection to a group. - Answers False True or False? The presence of an infectious agent is a sufficient cause for outbreaks of infectious disease to occur. - Answers False An attack rate is an alternative incidence rate that is used when: - Answers All the above Schistosomiasis is an example of: - Answers biological agents-helminth True or False? An enzootic disease among animals is similar to an endemic disease among humans. - Answers True A person with an inapparent infection: - Answers can transmit the infection to others True or False? Antigenicity of an infectious agent is measured by the secondary attack rate. - Answers False Which of the following examples involves indirect transmission of disease? - Answers A and B True or False? Physical environmental factors in the natural history of disease include weather, temperature, and biologic components. - Answers False True or False? If a disease is fatal, virulence can be measured by the case fatality rate. - Answers True An outbreak of salmonellosis occurred after an epidemiology department luncheon, which was attended by 485 faculty and staff. Assume everyone ate the same food items. Sixty-five people had fever and diarrhea, five of these people were severely affected. Subsequent laboratory tests on everyone who attended the luncheon revealed an additional 72 cases. The attack rate of salmonellosis was: - Answers 28.2% What factors comprise the epidemiologic triangle? - Answers All of the above The death rate per 100,000 for lung cancer is 7 among non-smokers and 71 among smokers. The death rate per 100,000 for coronary thrombosis is 422 among non-smokers and 599 among smokers. The prevalence of smoking in the population is 55%. The population etiologic fraction of disease due to smoking is: - Answers 0.83 for lung cancer and 0.18 for coronary thrombosis. Refer to the 2 by 2 table below. Assuming that the sample table is for a cohort study, define the risk difference or attributable risk: - Answers NOT THE ANSWER B. (A/A+B) / (C/C+D) The population etiologic fraction is a measure of the proportion of the disease rate in a population attributable to the exposure of interest. This measure of effect is influenced by: - Answers A and C True or False? The term attributable risk is defined as the ratio of the incidence of a disease among exposed individuals to the incidence among non-exposed individuals. - Answers False A causal association between factor and outcome can refer to - Answers Both C and D True or False? The term attributable risk is also known as the rate difference or risk difference. - Answers True The death rate per 100,000 for lung cancer is 7 among non-smokers and 71 among smokers. The death rate per 100,000 for coronary thrombosis is 422 among non-smokers and 599 among smokers. The prevalence of smoking in the population is 55%. The relative risk of dying for a smoker compared to a non-smoker is: [Refer to the chapter titled "Study Designs: Cohort Studies"] - Answers 10.1 for lung cancer and 1.4 for coronary thrombosis. The population etiologic fraction for a particular disease from Factor X alone is five times greater than that from Factor Y alone. If the relative risk associated with Factor X is 2, and with Factor Y is 20, which of the following statements is true? - Answers Fewer persons are exposed to Factor Y than to Factor X. The death rate per 100,000 for lung cancer is 7 among non-smokers and 71 among smokers. The death rate per 100,000 for coronary thrombosis is 422 among non-smokers and 599 among smokers. The prevalence of smoking in the population is 55%. Among smokers, the etiologic fraction of disease due to smoking is: - Answers 0.90 for lung cancer and 0.29 for coronary thrombosis. When assessing a positive relationship between alcohol consumption and oral cancer using a case-control study, increasing the sample size of the study will result in which of the following? i. A lower p value ii. A greater odds ratio iii. A smaller 95% confidence interval iv. A higher disease prevalence Circle the best response. - Answers None of the above. see page 422 The death rate per 100,000 for lung cancer is 7 among non-smokers and 71 among smokers. The death rate per 100,000 for coronary thrombosis is 422 among non-smokers and 599 among smokers. The prevalence of smoking in the population is 55%. On the basis of the relative risk and etiologic fractions associated with smoking for lung cancer and coronary thrombosis, which of the following statements is most likely to be correct? - Answers Smoking seems much more likely to be causally related to lung cancer than to coronary thrombosis. The purpose of a double-blind study is to: - Answers avoid observer and interviewee bias. A double-blind study of a vaccine is one in which: - Answers neither observers nor subjects know which subject receives the vaccine and which receives a placebo. True or False? The purpose of matching in a case-control study is to select the controls in such a way that the control group has the same distribution as the cases with respect to certain confounding variables. - Answers True Which of the following is not a method for controlling the effects of confounding in epidemiologic studies? - Answers Blinding The strategy which is not aimed at reducing selection bias is: - Answers standardized protocol for structured interviews. In a survey which uses lay interviewers to interview one person about his or her health and the health of household members, the sources of error include: - Answers All the above An epidemiologic experiment is performed in which one group is exposed to a suspected factor and the other is not. All individuals with an odd hospital admission number are assigned to the second group. The main purpose of this procedure is to: - Answers improve the likelihood that the two groups will be comparable with regard to known and unknown confounding factors In a study to determine the incidence of a chronic disease, 150 people were examined at the end of a three-year period. Twelve cases were found, giving a cumulative risk of 8%. Fifty other members of the initial cohort could not be examined; 20 of these 50 could not be examined because they died. Which source of bias may have affected the study? - Answers Selection bias: survival bias You are investigating the role of physical activity in heart disease and suggest that physical