Discuss the major problem resulting from the lack of randomization in a cohort

Discuss the major problem resulting from the lack of

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15. Discuss the major problem resulting from the lack of randomization in a cohort study? [ONE POINT]Without randomization, the study might take a lot of time to carry out. 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. Discuss what is the study design used in this study? [ONE POINT] Field trial: The study involved people who were healthy but were pre-summed to be at risk of cholera. 17. It has been suggested that physicians may examine women who use oral contraceptives more often or more thoroughly than women who do not. If so, and if an association is observed between phlebitis and oral contraceptive use, could this association be due to bias? What could be the type of bias in this study? [ONE POINT] The association of OC and phlebitis could be as a result of bias because the increased examination by the physicians who are aware that their patients have been exposed to OC. This is surveillance bias: occurs when the group with the known exposure are followed more closely (La Torre, 2010). Question 18 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.
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APPLIED EPIDEMIOLOGY 9 18. Based on the description given above, what source of bias is least likely to be present in this study? [ONE POINT] a.Recall biasb.Bias due to loss of subjects from the control group over timec.Bias due to controls being non-representative of the non-diseased populationd.Bias due to use of different methods of ascertainment of exposure in the cases and controlse.Selection bias for exposure to x-ray therapy in the pastAnswer: (b); in a cohort study, bias can result from the cohorts having unequal losses to follow-up. 19. Data for the case-control study were obtained from hospitalized patients in London and vicinity over a 4-year period (April 1948 – February 1952). Initially, 20 hospitals, and later more, were asked to notify the investigators of all patients admitted with a new diagnosis of lung cancer. These patients were then interviewed concerning smoking habits, as were controls selected from patients with other disorders (primarily non-malignant) who were hospitalized in the same hospitals at the same time.
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