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Mann-Whitney U test

Mann-Whitney U test. Mann-Whitney U test. Push this to sort the data in an ascending order. Mann-Whitney U test. Rank both lists as one combined list I found this a time consuming task. Mann-Whitney U test. Sum the ranks for each sample N1= # obs in 1 N2= # obs in 2.

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Mann-Whitney U test

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  1. Mann-Whitney U test

  2. Mann-Whitney U test Push this to sort the data in an ascending order

  3. Mann-Whitney U test • Rank both lists as one combined list • I found this a time consuming task

  4. Mann-Whitney U test • Sum the ranks for each sample • N1= # obs in 1 N2= # obs in 2

  5. Mann-Whitney U test • Normally you would now use the formula’s and chart in the Brown reading. • U1=(N1)(N2)+[(N1)(N1+1)]/2 – R1 U1=124.4 • U2=(N1)(N2)+[(N2)(N2+1)]/2 – R2 U2=128.2 • However the sample size is larger than the table will allow because any sample greater than 20 can be assumed to mimic normality • We therefore use the equation to convert the U statistic to a Z- score.

  6. Mann-Whitney U test • N1=10 • N2=10 • U1=124.4 • U2=128.2 • Z = {largest U value – [N1*N2]/2} (N1)(N2)(N1+N2+1)]/12 • Z = 5.9 • If Z > 1.96 than P < 0.05 • Therefore there is a significant difference between the thorax width of single and mated males

  7. Wilcoxon Signed Rank • When N>15 use a z score conversion • µT+ = N(N+1)/4 • VarT+ = N(N+1)(2N+1)/24 • Z = T+ - µT+ / VarT+ • = T+ - [N(N+1)/4] [N(N+1)(2N+1)/24] • If Z > 1.96 than P < 0.05 • reject null hypothesis

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