unit 4 answers

unit 4 answers - Unit 4 Practice Questions Epidemiology...

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Unit 4 Practice Questions Epidemiology 6000 A case-control study of 1700 participants looked at the association between Tamoxifen and uterine cancer. The study included 689 cases. There were 139 cases and 58 controls taking Tamoxifen. Fill in the 2x2 table below. Uterine Cancer Tamoxife n Yes No Yes 139 58 No 550 953 1a. Calculate the odds ratio of the above study. OR = ) 550 * 58 ( ) 953 * 139 ( = 4.15 1b. Interpret the measure of association. The odds ratio is greater than 1.0, therefore Tamoxifen is a risk factor for uterine cancer. People that use Tamoxifen have a 4.15 times greater risk of developing uterine cancer compared to people who do not take Tamoxifen. 2. The Nurse’s Health Study followed more than 120,000 women for several decades. During the follow-up period 1500 women developed melanoma. Researchers sent questionnaires to the 1500 cases and a control group made up of 3000 other study participants, to collect additional information about exposures possibly associated with melanoma. What type of study design is this? a. Case-cohort b. Case-crossover c. Nested case-control d. Retrospective cohort 3. Which of the following is characteristic of a case-crossover study? a. Each person serves as their own control. b. Controls are a random sample selected at the beginning of a cohort study. c. The study is conducted within a cohort study d. Both a and c
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4. Calculate the odds ratio for the following matched pairs case-control study. 200 pairs where the case is exposed and the control is not. 50 pairs where the control is exposed and the case is not. 130 pairs where cases and controls are exposed. 85 pairs where cases and controls are unexposed. Controls Cases Exposed Unexposed Exposed 130 200 Unexposed 50 85 OR = b/c = 200/50 = 4 5. Which of the following are disadvantages of the case-control study design? (check all that apply) Cannot calculate relative risk directly Cannot determine the odds ratio Cannot determine prevalence Expensive to conduct Generally not good for studying rare exposures Not good for studying rare disease Relatively long time required to complete study Relies on recall or existing records Selection of controls may be difficult Usually requires a relatively large number of subjects 6. Name the bias that may arise from the situations described below: A case is more motivated to participate than a control, and thus more likely to report past exposures accurately Recall Bias An interviewer learns to distinguish cases from controls, and subsequently differs slightly between them in how she asks her questions. Observer Bias (also called interviewer bias) 7. In a sentence or two, describe why sampling incident cases is better than sampling
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unit 4 answers - Unit 4 Practice Questions Epidemiology...

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