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:
| Cannot be determined from the information provided. | ||
| 0.83 for lung cancer and 0.18 for coronary thrombosis. | ||
| 0.80 for lung cancer and 0.18 for coronary thrombosis. | ||
| 0.83 for lung cancer and 0.28 for coronary thrombosis. | ||
| 0.80 for lung cancer and 0.28 for coronary thrombosis. |
| SAMPLE 2 BY 2 TABLE | |||
| Outcome | Total | ||
| Factor | + | − | |
| + | A | B | A + B |
| − | C | D | C + D |
| Total | A + C | B + D | A + B + C + D |
Assuming that the sample table is for a cohort study, define the risk difference or attributable risk.
| (A/A+C) / (B/B+D) | ||
| (A/A+B) / (C/C+D) | ||
| (A/A+C) − (B/B+D) | ||
| (A/A+B) – (C/C+D) | ||
| None 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%.
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?
| No comparative statement is possible between smoking and lung cancer or coronary thrombosis. | ||
| Smoking seems much more likely to be causally related to lung cancer than to coronary thrombosis. | ||
| Smoking seems much more likely to be causally related to coronary thrombosis than to lung cancer. | ||
| Smoking does not seem to be causally related to either lung cancer or coronary thrombosis. | ||
| Smoking seems to be equally causally related to lung cancer and coronary thrombosis. |
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:
| RESULTS OF DIAGNOSIS | ||
| TEST RESULTS | Disease Present | Disease Absent |
| Positive for Factor X | 40 | 60 |
| Negative for Factor X | 10 | 140 |
The specificity of this test is expressed as:
| 7% | ||
| 80% | ||
| 70% | ||
| 56% | ||
| 30% |
Sensitivity and specificity of a screening test refer to its:
| Reliability | ||
| Validity | ||
| Yield | ||
| Repeatability | ||
| None of the above |
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. | ||
| They cannot improve this test and should begin work developing a new test. | ||
| Test each person’s blood twice. | ||
| Rise the cut point above 50 units. |
The figure on page 475 represents different combinations and qualities of validity and reliability (high vs. low).
Which set of symbols represents high reliability?
| A | ||
| Both A and C | ||
| B | ||
| None of the above | ||
| C |
Choose the best answer. A test developed to assess age-related changes in bone density that does not pick up these changes has:
| None of the options listed here. | ||
| low concurrent validity | ||
| Low construct validity | ||
| Low predictive validity |