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Unformatted text preview: Public Health 6450 Fall 2011 Lynn Eberly and Andy Mugglin Division of Biostatistics School of Public Health University of Minnesota ph6450@biostat.umn.edu Part 17 Review Paired Samples in TwobyTwo Tables Where are we going? Previously: I Chisquare tests for H : independence in twobytwo tables (Ch. 9.19.2) I Chisquare tests for H : p 1 = p 2 in twobytwo tables (Ch. 9.2) I Chisquare tests for larger tables (Ch. 9.19.2) Current topics: I Chisquare tests for paired sample twobytwo tables (not in M,M&C) I Binomial exact test for paired sample twobytwo tables (not in M,M&C) Next topics (after Exam II): I Overview of Analysis Methods (so far) I Describing Relationships Between Quantitative Variables Eberly and Mugglin PubH 6450 Fall 2011 Part 17 2 / 22 Review Paired Samples in TwobyTwo Tables Motivating the chisquare test McNemars test for paired twobytwo tables Detailed Example The Binomial exact test for paired two by two tables Paired Samples and Binomial Outcomes I Recall that paired samples have two measures taken on one unit. I For continuous measures, such studies may collect, for example: I a before and after measure of a test score with a new teaching intervention (unit = student) I a depression scale taken on each of two twins (unit = twin pair) I packyears of cigarette smoking for each of a lung cancer case and a matched control (unit = case with matched control). In this section, we are concerned with two measures that are binary and are taken on the same unit. Eberly and Mugglin PubH 6450 Fall 2011 Part 17 3 / 22 Review Paired Samples in TwobyTwo Tables Motivating the chisquare test McNemars test for paired twobytwo tables Detailed Example The Binomial exact test for paired two by two tables Nonfat versus Whole Fat Yogurt Participants in a nutrition survey each answered two questions: Does whole fat yogurt taste good or bad to you? Does nonfat yogurt taste good or bad to you? Nonfat Whole Fat Good Bad Total Good 55 12 67 Bad 5 28 33 Total 60 40 100 This is a matched pairs study: each participant was asked both questions, and thus was matched to him or herself. How many participants? How many pairs? Eberly and Mugglin PubH 6450 Fall 2011 Part 17 4 / 22 Review Paired Samples in TwobyTwo Tables Motivating the chisquare test McNemars test for paired twobytwo tables Detailed Example The Binomial exact test for paired two by two tables Subsequent Surgery after Initial Sinus Surgery Patients undergoing bilateral sinus surgery for chronic rhinosinusitis may have one side (e.g., left) treated with Treatment A and the other (e.g., right) with Treatment B to see if A is better than B at preventing subsequent surgeries within a 12month period of time....
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 Fall '10
 AndyMugglin

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