unit 7 additional answers - Unit 7 Fall 2010...

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Click to edit Master subtitle style Unit 7 Fall 2010 Questions and Answers
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n Definition of bias n Common types of biases n Selection bias in cohort and case-control studies n Observational/information biases: surveillance,  recall, interviewer, item non-response n Most important biases in cohort studies n Most important biases in case-control/cross- sectional studies n Biases in analytic phases of a study n Misclassification: Differential and non-differential  and their effects on the RR/OR n Ways to avoid bias Study guide – Unit 7
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2x2 re-arrangement (from Unit 5) Case Control Men 53 83 136 Women 36 80 116 89 163 252 OR = 4240/2988 = 1.42 Case Control Women 36 80 116 Men 53 83 136 89 163 252 OR = 2988/4240 = 0.705 Note: 1/1.42 = 0.705
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Chance is random error http://www.dorak.info/epi/bc.html 
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Errors of chance will cancel each other out when N is increased n Errors in chance lead to imprecise results
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Bias is systematic error http://www.dorak.info/epi/bc.html 
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Errors of bias can not be eliminated by sample size n Errors of bias lead to inaccurate (wrong) results n It is the investigator’s responsibility  to minimize  or eliminate errors of bias in the: Design Implementation Data collection Data cleaning Data analysis Manuscript preparation and submission
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Which types of biases are not the responsibility of the investigator? n Misclassification bias n Recall bias n Selection bias n Unknown confounding bias
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Which types of biases are not the responsibility of the investigator? n Misclassification bias n Recall bias n Selection bias n Unknown confounding bias
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Bias is often defined as any systematic error that occurs in a study and alters This systematic error may occur… n A. In the design phase of the study n B. In the conduct of the study n C.In the analysis of the study n D.All of the above
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Bias is often defined as any systematic error that occurs in a study and alters its results. This systematic error may occur… n A. In the design phase of the study n B. In the conduct of the study n C.In the analysis of the study n D.All of the above
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Define Selection Bias n Type your answer here
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Define Selection Bias n An error due to systematic differences in characteristics between those who are selected for study and those who are not (Last J, 1995) Different criteria are used to enroll (select) participants in an investigation Subjects come from different underlying populations (po incorrect in controls; exposed/ unexposed in multi-cohort study) in a way that is related to E/D status
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Set up a 2x2 for the following hypothetical scenario n Consider a study of family history (FH)  of breast cancer (E) and risk of breast  cancer (D). Suppose 300 incident  cases of breast cancer (D) were  identified at Moffitt Cancer Center, and  300 controls were identified from 
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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 7 additional answers - Unit 7 Fall 2010...

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