LectureNov17

LectureNov17 - BME 423 Lecture Notes - Nov. 17, 2008...

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1 Methods Based on Ranks – Nonparameteric Methods BME 423 Lecture Notes - Nov. 17, 2008 IV Handling Ties for Mann-Whitney & Wilcoxin V. Kruskal-Wallis: 3 or More Groups, Different Subjects A. Idea B. Procedure C. Example VI. Friedman Statistic: 3 or More Groups, Same Subjects A. Idea B. Procedure C. Example Glantz Chapt. 10, pp 386-390, 395-401
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2 Mann-Whitney Rank-Sum – Two Different Groups Make inferences based on Rank. T – Sum of Ranks in Smaller Group will be used as the Test Statistics Mann-Whitney Rank-Sum Procedure 1. Rank all observations in ascending order regardless of group (ties ). 2. Compute T – sum of ranks in smaller group. 3. Comparer T to its critical values a. use T statistic table b. use Normal distribution pdf of T 8 B N 8 B N > 2 (, ) TT N μ σ () 2 1 + + = B s s T n n n 1 12 sB s B T nn n n + + = 1 2 T T T T z −− = Tc r i t i c a l zz > Reject H0 (Special case needed when ties occur)
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3 Mann-Whitney Rank-Sum Procedure Rank all observations in ascending order regardless of group (ties ). Tied observations assigned same rank, equal to the average of ranks they would have been assigned if not ties has occurred.
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This note was uploaded on 12/02/2008 for the course BME 423 taught by Professor D'argenio during the Fall '06 term at USC.

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LectureNov17 - BME 423 Lecture Notes - Nov. 17, 2008...

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