In a case-control study, 10% of the exposed cases and 25% of the exposed controls are mistakenly classified as non-exposed. This is an example of O Ecological fallacy O Positive predictive value O Positive Confounding O Selection bias O Differential misclassification of disease O Intention to treat O Negative Confounding O Differential misclassification of exposure O Randomization O Random error O Non-differential misclassification of exposure O Non-differential misclassification of disease
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In a case-control study, researchers compare individuals with a certain condition (cases) to those without it (controls) to identify potential risk factors or exposures. Show more…
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1. If a subjects' willingness to participate is related to both their exposure status and disease status, the resulting bias is known as: (1 point) a. control-selection bias. b. interviewer/recording bias. c. self-selection bias. d. surveillance, diagnostic, or referral bias. 2. Differential misclassification can bias study results in which direction? (1 point) a. Towards the null b. Away from the null c. Either towards or away from the null 3. Non-differential misclassification tends to bias study results in which direction? (1 point) a. Towards the null b. Away from the null c. Either towards or away from the null 4. A case-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. Two hundred (200) cases with brain cancer were identified from the state cancer registry, and 200 controls were recruited from the same neighborhoods where the cases lived. The mothers of the children completed a questionnaire that asked them to describe their child's past history of head injury. The investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of the cases while a past history of head injury was reported in 30 of the controls. What type of bias was likely to have influenced the findings of this study? (1 point) a. Length bias b. Recall bias c. Surveillance, diagnostic, or referral bias d. Interviewer/recorder bias 5. For a variable to be a confounder, it must: (1 point) a. be a predictor of the disease (outcome) under study. b. be associated with the risk factor (exposure) under study. c. not be in the causal pathway between exposure and outcome. d. All of the above
Adi S.
35. An epidemiologist was interested in determining whether aspirin was associated with an increased risk of gastrointestinal (GI) bleeding. She relied on primary physicians to identify 600 patients at a hospital who were taking a daily dose of aspirin and 600 other patients who were not taking aspirin. Subjects were followed for 1 year to detect any occurrences of GI bleeding in this cohort study. Due to publicity about the risk of bleeding associated with aspirin, primary physicians treating patients at the hospital followed their patients who were taking aspirin more closely than they were unexposed subjects. Which of the following describes the impact that this may have on the epidemiologist’s study? (3 points) A. Would introduce recall bias B. Would result in differential classification of exposure C. Would result in differential classification of outcome D. Would result in nondifferential classification of exposure E. Would result in nondifferential classification of outcome
James K.
a) In a case-control study of the relationship between herbicide exposure and non-Hodgkin's lymphoma, the investigators found a very strong relationship between prior herbicide exposure and non-Hodgkin's lymphoma. However, after the study was complete, the investigator learned that people in the case group were more likely to be classified as being exposed to herbicides, especially if information on exposures in this group was obtained from a spouse. Over-reporting of herbicide exposure was not a problem in the control group, since all control participants self-reported information on past herbicide exposure. A. Information Bias B. Selection Bias C. Confounding D. Random Error b) Which of the following is the correct reason for the observed bias or error in part a: A. The underreporting of exposure status in the case group suggests that exposure may have been misclassified more often in the case group than in the control group. This represents differential misclassification, which is a consequence of information bias. B. The underreporting of exposure status in the control group was the same as that in the case group. This represents non-differential misclassification, which is a consequence of information bias. C. The over-reporting of exposure status in the case group suggests that exposure may have been misclassified more often in the case group than in the control group. This represents differential misclassification, which is a consequence of information bias. D. The over-reporting of exposure status in the case group suggests that exposure may have been misclassified more often in the case group than in the control group. This represents non-differential misclassification, which is a consequence of information bias. c) Please indicate the probable direction of bias for the observed study results compared to the true association one would expect in the underlying population for part a: A. Negative B. Positive C. We are not able to determine the direction of the bias.
Sri K.
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