HLTH 503 Final: Cumulative Quiz questions

A case-control study is purely a descriptive (as opposed to analytic) study designA case-control study is purely a descriptive (as opposed to analytic) study design - False A cross-sectional study allows the demonstration of a time sequence between exposure and disease. - False A double-blind study of a vaccine is one in which: - neither observers nor subjects know which subject receives the vaccine and which receives a placebo. A major advantage of community trials is that they are: - able to estimate directly the realistic impact of behavior change 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? - The prevalence of virus X infection is higher among the hospital patients than among blood donors A new blood test has been developed to screen for disease Z. Researchers establish 50 units as a cut point above which a test is considered positive and thereby indicative of disease. The test manufacturers determine that the test's sensitivity is unacceptably low. However, the manufacturers are not concerned with the specificity and do not want the cost of the test to rise. How can they improve the sensitivity of the test? - Lower the cut point below 50 units. 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 valueThe number of false positives is: - 81