Question 12 (1 point) What are the public health and/or policy implications of the apparently protective effect of oral contraceptives on ovarian cancer? It would be appropriate to go over the benefts of OC and at the same time the risk of using OC which includes the side effects which varies from every individual. Taking OC can cause blood clots in some people and before taking any OC an individual has to make sure that there will be no harsh side effects on them that could trigger possible health problems.Part 2 – Types of Bias Confoundingis a bias that results when the risk factor being studied is so mixed up with other possible risk factors that its single effect is very difficult to distinguish. For example, it might be thought that smoking is a risk factor for heart disease, because people who are exposed to smoking have a higher occurrence of heart disease. However, the case is not quite so clear as it might appear. It turns out that people who smoke also drink alcohol—so is it the smoking, the alcohol or both that are responsible for heart disease? Unless these tangled effects are untangled with advanced mathematical methods (which, remember, we are not getting into), the association between smoking and heart disease, as measured using the relative risk formula we have, is probably too high or too low—that is, it is biased. Selection biasis a distortion in the estimate of association between risk factor and disease that results from how the subjects are selected for the study. Selection bias could occur because the sampling frame is sufficiently different from the target population or because the sampling procedure cannot be expected to deliver a sample that is a mirror image of the sampling frame. Information biasis a distortion in the estimate of association between risk factor and disease that is due to systematic measurement error or misclassifcation of subjects on one or more variables, either risk factor or disease status. It is important to realize that these errors are part of being human and they are not occurring because the physicians or researchers are not being sufficiently careful. It is not so much the random mismeasure or misdiagnosis of an individual that is problematic (although random errors in diagnosis will tend to bias the association toward a relative risk of 1.0, because the true association is diluted with noise). It is the method of measurement or classifcation that is the greater problem, because it systematically exerts an effect on each of the individual measurements in the sample. An investigator would like to assess the association of melanoma (skin cancer) and exposure to infrared skin tanning services by using a hospitalbased case–control study. Hospitalized individuals with ‐
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