Practice Questions 2
Answer all the questions and justify your answers.Total points=30(15% of the course grade)
1. All of the following are important criteria when making causal inferences except: [ONE POINT]
a. Consistency with existing knowledge
b. Dose-response relationship
c. Predictive value
d. Strength of association
e. Consistency of association in several studies
2. A case-control study is characterized by all of the following except: [ONE POINT]
a. It is relatively inexpensive compared with most other epidemiologic study designs
b. Incidence rates may be computed directly
c. Patients with the disease (cases) are compared with persons without the disease (controls)
d. Assessment of past exposure may be biased
e. Definition of cases may be difficult
Questions 3 refer to the following information:
OUTCOME AFTER 15 YRS
At Beginning of Study CHD Developed CHD Did Not Develop
2,000 Healthy smokers 70 1,930
4,000 Healthy nonsmokers 35 3,965
The results of a 15-year cohort study of smoking and coronary heart disease (CHD) are shown in the table above [TWO POINTS]:
3. What is the incidence of CHD in smokers that can be attributed to smoking?
4. Which of the following is a case-control study? [TWO POINTS]
a. Obtaining histories and other information from a group of known cases and from a comparison group to determine the relative frequency of a characteristic or
exposure under study
b. Study of past mortality or morbidity trends to permit estimates of the occurrence of disease in the future
c. Study of the incidence of cancer in men who have quit smoking
d. Analysis of previous research in different places and under different circumstances to permit the establishment of hypotheses based on cumulative knowledge of all
known factors
e. Both aand b
5. The study investigated the risk of heart disease by smoking status and found that the risk ratio is 3.5. Using your own words, interpret the risk ratio of 3.5.
[ONE POINT]
6. Several studies have found that approximately 90% of cases of lung cancer are due to cigarette smoking. This measure is an example of: [TWO POINT]
a. A relative risk
b.A prevalence risk
c. A proportionate mortality ratio
d. An attributable risk
e. An incidence rate
7. An advertisement in a medical journal stated that “2,000 subjects with sore throats were treated with our new medicine. Within 4 days, 94% were asymptomatic.”
The advertisement claims that the medicine was effective. Based on the evidence given above, the claim: [ONE POINT]
a. Is correct
b. May be incorrect because the conclusion is not based on a rate
c. May be incorrect because of failure to recognize a long-term cohort phenomenon
d. May be incorrect because no test of statistical significance was used
e. May be incorrect because no control or comparison group was involved
8. In a study of a disease in which all cases that developed were ascertained, if the relative risk for the association between a factor and the disease is equal
to or less than 1.0, then: [ONE POINT]
a. There is no association between the factor and the disease
b. There is either no association or a negative association between the factor and the disease
c. Either matching or randomization has been unsuccessful
d. The factor protects against development of the disease
e. The comparison group used was unsuitable, and a valid comparison is not possible
9. Ecologic fallacy refers to: [ONE POINT]
b. Assessing outcome in large groups rather than in many small groups
a. Assessing exposure in large groups rather than in many small groups
c. Failure to examine temporal relationships between exposures and outcomes
d. Ascribing the characteristics of a group to every individual in that group
e. Examining correlations of exposure and outcomes rather than time trends
10. Assume that early detection of disease X through screening improves prognosis. In order for a screening program to be most effective, at which point in the
natural history in the diagram must the critical point be? [ONE POINT]
a. Between A and B
b. Between C and D
c. Anywhere between A and D
d. Between B and C
e. Anywhere between A and C
11. A study to assess the relationship between smoking and lung cancer found that the odds ratio is 4. Using your own words, interpret the odds ratio. [ONE POINT]
12. All of the following are measures of process of health care in a clinic except: [ONE POINT]
a. Proportion of patients in whom blood pressure is measured
b. Proportion of patients advised to stop smoking
c. Proportion of patients whose bill is reduced because of financial need
d. Proportion of patients who have complications of a disease
13. In a case-control study, which of the following is true? [ONE POINT]
a. The proportion of cases with the exposure is compared with the proportion of controls with the exposure
b. Disease rates are compared for people with the factor of interest and for people without the factor of interest
c. The investigator may choose to have multiple comparison groups
d. Recall bias is a potential problem
e. a, c, and d
14. Which of the following is not an advantage of a prospective cohort study? [ONE POINT]
a. Precise measurement of exposure is possible
b. It usually costs less than a case-control study
c. Recall bias is minimized compared with a case-control study
d. Incidence rates can be calculated
e. Many disease outcomes can be studied simultaneously
15. Which of the following is an approach to handling confounding? [ONE POINT]
a. Individual matching
b. Stratification
c. Group matching
d. Adjustment
e. All of the above
16. Residents of three villages with three different types of water supply were asked to participate in a survey to identify cholera carriers. Because several
cholera deaths had occurred recently, virtually everyone present at the time underwent examination. The proportion of residents in each village who were carriers was
computed and compared. What is the proper classification for this study? [TWO POINTS]
a. Case-control study
b.Cohort study
c. Cross-sectional study
e. Experimental study
Question 17 is based on the information given below:
In a case-control study of the relationship of radiation exposure and thyroid cancer, 50 cases admitted for thyroid cancer and 100 “controls” admitted during the same
period for treatment of hernias were studied. Only the cases were interviewed, and 20 of the cases were found to have been exposed to x-ray therapy in the past, based
on the interviews and medical records. The controls were not interviewed, but a review of their hospital records when they were admitted for hernia surgery revealed
that only 2 controls had been exposed to x-ray therapy in the past.
17. Based on the description given above, what source of bias is least likely to be present in this study? [ONE POINT]
a. Recall bias
b. Bias due to controls being nonrepresentative of the nondiseased population
c. Bias due to loss of subjects from the control group over time
d. Bias due to use of different methods of ascertainment of exposure in the cases and controls
e. Selection bias for exposure to x-ray therapy in the past
18. Of 3,000 persons who had received radiation treatment in childhood because of an enlarged thymus, cancer of the thyroid developed in 30 and a benign thyroid
tumor developed in 60. A comparison group consisted of 5,100 children who had received no such treatment (brothers and sisters of the children who had received
radiation treatment). During the follow-up period, none of the comparison group developed thyroid cancer, but benign thyroid tumors developed in 10. Calculate the
relative risk for benign thyroid tumors [TWO POINTS]: _______________________
19. The extent to which a specific health care treatment, service, procedure, program, or other intervention produces a beneficial result under ideal controlled
conditions is its [ONE POINT]:
a. Efficiency
b. Effectiveness
c. Effect modification
d. Efficacy
e. None of the above
20. The extent to which a specific health care treatment, service, procedure, program, or other intervention does what it is intended to do when used in a
community-dwelling population is termed its: [TWO POINTS]
a. Effect modification
b. Efficiency
c. Effectiveness
d. Efficacy
e. None of the above
21. The best index (indices) for concluding that an early detection program for breast cancer truly improves the natural history of disease, 10 years after its
initiation, would be [TWO POINTS]:
a. A decrease in the prevalence of breast cancer
b. A smaller proportionate mortality for breast cancer 10 years after initiation of the early detection program compared to the proportionate mortality prior to its
initiation
c. A decrease in incidence of breast cancer
d. Improved long-term survival rates for breast cancer patients (adjusted for lead time)
e. None of the above
22. In general, screening should be undertaken for diseases with the following feature(s) [TWO POINTS]:
a. Diseases with a low prevalence in identifiable subgroups of the population
b. Diseases for which case-fatality rates are low
c. Diseases that are readily diagnosed and for which treatment efficacy has been shown to be equivocal in evidence from a number of clinical trials
d. Diseases with a natural history that can be altered by medical intervention
e. None of the above
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