Understanding Absolute and Relative Effects in Epidemiology

Correct answers are hidden. Score for this quiz: 71.25 out of 75 Submitted Feb 17 at 10:37am This attempt took 20 minutes. Question 1 3.75 / 3.75 pts 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. True False Question 2 3.75 / 3.75 pts 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: 0.90 for lung cancer and 0.88 for coronary thrombosis. 0.90 for lung cancer and 0.29 for coronary thrombosis. 0.89 for lung cancer and 0.88 for coronary thrombosis. 0.89 for lung cancer and 0.29 for coronary thrombosis. cannot be determined from the information provided.

Question 3 3.75 / 3.75 pts 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? Smoking seems much more likely to be causally related to coronary thrombosis than to lung cancer. Smoking seems much more likely to be causally related to lung cancer than to coronary thrombosis. Smoking seems to be equally causally related to lung cancer and coronary thrombosis. Smoking does not seem to be causally related to either lung cancer or coronary thrombosis. No comparative statement is possible between smoking and lung cancer or coronary thrombosis. Question 4 3.75 / 3.75 pts 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.

i and iii only ii and iv only i, ii, and iii only All of the above None of the above Page: 422 Question 5 3.75 / 3.75 pts 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: the relative risk of the disease in exposed individuals versus unexposed individuals. the prevalence of the disease in the population. the prevalence of the exposure in the population. A and B A and C

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Question 6 3.75 / 3.75 pts 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: (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 Question 7 3.75 / 3.75 pts 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:

0.80 for lung cancer and 0.28 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. 0.83 for lung cancer and 0.18 for coronary thrombosis. cannot be determined from the information provided. Page: 418, formula 4 Question 8 3.75 / 3.75 pts 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”] 9.1 for lung cancer and 0.30 for coronary thrombosis. 9.1 for lung cancer and 1.4 for coronary thrombosis. 10.1 for lung cancer and 8.4 for coronary thrombosis. 10.1 for lung cancer and 1.4 for coronary thrombosis. 12.4 for lung cancer and 1.7 for coronary thrombosis.

Question 9 3.75 / 3.75 pts 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? The risk of developing the disease is greater in those exposed to Factor X only than in those exposed to Factor Y only. Fewer persons are exposed to Factor Y than to Factor X. The proportion of the disease in the population attributable to Factor Y is greater than that attributable to Factor X. More persons are exposed to Factor Y than to Factor X. The risk of developing the disease for persons exposed to Factor Y is five times greater than for persons exposed to Factor X. Question 10 3.75 / 3.75 pts True or False? The term attributable risk is also known as the rate difference or risk difference. True False Question 11

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3.75 / 3.75 pts A causal association between factor and outcome can refer to Statistical independence Secondary association Indirect association Direct association Both C and D Question 12 3.75 / 3.75 pts Which of the following is not a method for controlling the effects of confounding in epidemiologic studies? Randomization Stratification Matching Blinding Restriction

Question 13 3.75 / 3.75 pts 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: ensure a double-blind study. prevent observer bias with respect to the factor. prevent observer bias with respect to the outcome. improve the likelihood that the two groups will be comparable with regard to known and unknown confounding factors. guarantee comparability of the two groups with regard to other relevant factors. Question 14 3.75 / 3.75 pts 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? Information bias: interviewer/abstractor bias Hawthorne effect Selection bias: survival bias

Information bias: recall bias Question 15 3.75 / 3.75 pts The purpose of a double-blind study is to: achieve comparability of cases and controls. reduce the effects of sampling variation. avoid observer and interviewee bias. avoid observer bias and sampling variation. avoid interviewee bias and sampling variation. Question 16 3.75 / 3.75 pts You are investigating the role of physical activity in heart disease and suggest that physical activity protects against having a heart attack. While presenting these data to your colleagues, someone asks if you have thought about confounders such as factor X. This factor X could have confounded your interpretation of the data if it: is a factor for some other disease, but not heart disease. is a factor associated with physical activity and heart disease.

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is a part of the pathway by which physical activity affects heart disease. has caused a lack of follow-up of test subjects. Question 17 3.75 / 3.75 pts The strategy which is not aimed at reducing selection bias is: development of an explicit case definition. encouragement of high participation rates. standardized protocol for structured interviews. enrollment of all cases in a defined time and region. Question 18 3.75 / 3.75 pts 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. True False Incorrect Question 19 0 / 3.75 pts A double-blind study of a vaccine is one in which:

the study group receives the vaccine and the control group receives a placebo. neither observers nor subjects know the nature of the placebo. neither observers nor subjects know which subject receives the vaccine and which receives a placebo. – CORRECT ANSWER neither the study group nor the control group knows the identity of the observers. the control group does not know the identity of the study group. Question 20 3.75 / 3.75 pts 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: the person with disease has had no symptoms and is not aware of the disease. the respondent provides the information but the interviewer doesn't record it or records it incorrectly. the interviewer doesn't ask the questions that he or she is instructed to ask, or asks them incorrectly. the person has had symptoms and has had medical attention but does not know the name of the disease.

all of the above Quiz Score: 71.25 out of 75

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Quiz Absolute and Relative Effects

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