1. Calculate the odds ratio. 2. To see if smoking is a confounder, we can check the three properties of a confounder in
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1. Calculate the odds ratio. 2. To see if smoking is a confounder, we can check the three properties of a confounder in
question we ask is: Is smoking associated with diabetes in the controls? Here are the data for controls only in a 2x2 table with smoking (counfounder) CONTROLS ONLY (D-) Smokers (C+) Non-smokers (C-) Total Diabetes + (E+) 15 16 31 Diabetes (E-) 155 1426 1581 a) What is the prevalence of smoking in controls with diabetes? b) What is the prevalence of smoking in controls without diabetes? c) Is the prevalence of smoking different for diabetes and non- diabetes? What is the ratio of these two prevalences? d) Is smoking associated with diabetes in controls?
1. Calculate the odds ratio. 2. To see if smoking is a confounder, we can check the three properties of a confounder in our data. PROPERTY 1: Is the prevalence of smoking different between our exposed and unexposed groups? We must look at this association in the ABSENCE of disease (i.e. in our control group) because we know that smoking may be a cause of MI (the outcome). Hence the