Wilcoxon matched-pairs signed test

If a normal distribution is not assumed, the Wilcoxon matched-pairs signed-ranks test can be used to test Ho = p,d = 0. 

The choice of an appropriate statistical method is important, and a method suitable for the comparison of two groups in terms of an ordinal outcome measurement is the Mann-Whitney/Wilcoxon rank-sum test (not to be confused with the Wilcoxon matched-pairs signed ranks test, which is appropriate for paired data - see later). It is both inefficient and inappropriate to use a qualitative data test (such as a simple chi-square) for such a measurement, and the application of quantitative data tests (such as one of the f-tests) is also invalid. 

Twenty trials were performed in each experiment (Experiment 1 male vs. female Experiment 2 gravid vs. non-gravid). There was no significant difference in the mean time spent in either stimulus area for the test males (Wilcoxon matched pairs signed ranks test Experiment 1 T=1.122, P=0.262 Experiment 2 T=0.934, P=. 350). Also, no significant differences were found for the frequency observed in either side of the test chamber for the entire 10 minute period or for first choice by test males. 

Table 1. Preferences of three species of Plethodon in trials with two substrate-home odor choices. In each trial, the female or male was given a choice of two substrates marked by another salamander. Response to substrate was measured every two minutes for two hours (for a total of 60 observations). T is the value of the Wilcoxon matched-pairs signed-ranks test, p is the two-sided probability with significance of a <= 0.05 and a<=0.01. C = conspecific, H = heterospecific. For P. teyahalee, HI = P. shennani, H2 = P. montanus for P. shermani, HI = P. montanus, Hl-P. teyahalee and for P. montanus, HI = P. shermani, H2 = P. teyahalee...

Comparisons between the sexes with respect to the size of the sternal gland indicate that it is longer, wider, and thicker in males than in females (P < 0.05 for each measure, Mann-Whitney U test Table 1). The active surface areas compared in 22 heterosexual pairs by the Wilcoxon matched-pairs sign rank test show that the gland is also more active... 

P < 0.05, Wilcoxon matched-pairs signed-rank test. NS P > 0.05. 

Wilcoxon Signed Test n Also known as the Wilcoxon Signed Rank Test, the Wilcoxon Matched-Pairs Signed-Rank Test, or the Wilcoxon Rank Sum Test, and is a nonparametric test used to test the null hypothesis that the median of the difference between the values of pairs of elements from related samples or repeated measurements on the same sample, is zero. It is assumed that the observations are independent. The differences, Zi, between the pairs of random variables, (x,-, y,) are calculated as z,- = y,—x,- and the zero differences are disguarded. The remaining, M, differences are ranked... 

Significantly different from controls (P< 0. 05), Wilcoxon one-tailed Matched-pairs signed ranks test. 

Wilcoxon signed rank test (paired or matched pairs)... 

Wilcoxon Signed Rank Test is the technique tests whether the medians of two populations are the same, when the samples are not independent of each other. This test is comparable to the parametric matched-pairs test that we considered previously. Technique follows calculate the differences between the two sample values for each pair of observations, drop the zero values, of the n non-zero values, rank the absolute values of the differences and sum the ranks of the positive and negative differences separately. Let W be the sum of the positive ranks. 

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