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Question: week 4 odds ratio calculation amp interpretation odds ratios are...

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Week 4: Odds Ratio Calculation & Interpretation Odds ratios are used in case control studies to determine the odds of being exposed to a risk factor at some time in the past in people with a disease compared to the odds of being exposed to a risk factor at some time in the past in people without a disease. Disease Status: Participants are selected based on their disease status (present, absent) Exposure Status: Case-Control Studies look back in time to identify if participants with disease were exposed to a risk factor at some time in the past may explain why they have a disease now (exposed, not exposed) Odds ratios are computed to compare the expected associations having disease & being exposed -cell a not having disease & not being exposed-cell d . . with unexpected associations . having disease & not being exposed-cell c not having disease & being exposed-cell b Ods ratios are computed using 2 x 2 tables. Disease status is at the top: Exposure status is at the left side. The cells are labeled a (disease and exposure +), b (disease - and exposure +), e (disease + and exposure -), d (disease - and exposure-) Disease The equation for an odds ratio is Expected associations Unexpected associations axd Exposure bxc We expect that those with disease are exposed (cell a) and those without disease are not exposed (cell d) We dont expect that those with disease are not exposed (cell c) and those without disease are exposed (cell b) Hence, the equation for an odds ratio is listed above. Page 122-123 describes how to interpret the odds ratio. We are using the Exposure Odds Ratio. You should know how to interpret an exposure odds ratio using the terminology on page 124 of your textbook Confidence Interval Calculator Two htm
Problem 1-identifying risk factors for a stomach cancer. People have a diagnosis with stomach cancer and nobody knows what caused it. As an epidemiologist employed by a cancer center, you need to identify the strength of association for potential risk factors From reading the literature, you decide to test 3 potential risk factors family history of stomach cancer, male sex, and eating high salt and smoked foods You conduct 3 case-control studies Sample selection: You select 100 cases from a cancer registry with stomach cancer. As a comparison group, you select 100 controls without stomach cancer and with similar demographic characteristics to the cases Exposure 1: Family History In the 100 cases, 3 with stomach cancer had relatives with stomach cancer. In the 100 controls, 1 had a relative with stomach cancer What is the OR and 95% a for family history as a risk factor?(1 point). Create a 2 x 2 table and insert the correct values What is the interpretation of the exposure odds ratio using the eample on page 124 in the textbook? (2 points Exposure 2: Male Sex n the 100 cases, 21 with stomach cancer were men. In the 100 controls, 10 were men What is the OR and 95% a for male sex as a risk factor? (1 point). Create a 2 x 2 table and insert the correct values What is the interpretation of the esposure ods ratio using the esample on paige 124 in the testbook? poins) Exposure 3: Eating high salt and smoked foods In the 100 cases, 30 with stomoch cancer ate a high salt/smoked foods diet. in the 100 controls,6 ate o high salt/smoked foods diet What is the OR and 95% CI for diet as a risk factor? (1 point). Create a 2 x 2 table and insert the correct values What is the interpretation of the exposure odds ratio using the example on page 124 in the textbook? (2 points) Summary Conclusion: Which risk factors have strength of association? (1 point
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