unit 8 additional answers - Click to edit Master subtitle...

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Unformatted text preview: Click to edit Master subtitle style Unit 8 Fall 2010 Questions and Answers n Confounding • Definition and identification of confounding • Determining if a variable is a potential confounder • Ways to control for confounding and when: randomization, restriction, matching (design), stratification, multivariate analysis, direct and indirect standardization • Mantel-Haenszel OR/RR • OR for matched studies and McNemar’s test • Definition and mechanics of rate adjustment: direct and indirect n Effect modification • Definition and identification of effect modification • Understanding the difference between effect modification and confounding • Evaluation of effect-modification through stratified analysis Study Guide Confounding is: n Mixing of effects of extraneous factors with the effect of int erest. n Change in an effect measure upon stratification or adjustment for extraneous factors n Var iables that can cause or prevent the outcome of interest, are not int er mediat e var iables, and are associat ed with the exposure(s) under investigation Confounding is: n Mixing of effects of extraneous factors with the effect of interest. n Change in an effect measure upon stratification or adjustment for extraneous factors n Variables that can cause or prevent the outcome of interest, are not intermediate variables, and are not associated with the factor(s) under investigation n A nuisance effect that must be eliminated in order to obtain a more valid estimate of the effect measure n All of the above How do we identify whether confounding exists? n Know the literature well. • Understand what other risk factors are related to your outcome • Understand how other risk factors are related to your exposure • Figure out biologically plausible DAG. n Know your data well. • Perform univariate, bivariate analyses to characterize distributions of variables in each comparison group (or cohorts); ways that single variables are related to Which DAG shows E PCF D E D PCF PCF E D YES/ NO YES/ NO YES/ NO Which DAG shows confounding? E PCF D E D PCF PCF E D YES/ NO YES/ NO YES / NO Salt intake Hypertensio n Stroke PCF intermediate Hypertensio n Stroke Disability PCF occurs after E and D Smoking OC use Stroke Smoking related to OC and stroke n Smoking is associat ed with oral contraceptive use (say smokers are more likely to use OCs) – I N THE DATA SET n Smoking is an independent r isk factor for stroke (among non-OC users) n Smoking is not the result of OC use (PCF is not the result of E) (not an I s obesity associated with n Note: Hyper tension may be a PCF. n Draw the DAG and stat e the role of hyper t ension. I s obesity associated with cardiovascular mortality?...
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This note was uploaded on 07/15/2011 for the course PHC 6000 taught by Professor Staff during the Summer '08 term at University of South Florida - Tampa.

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unit 8 additional answers - Click to edit Master subtitle...

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