Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [wilcoxon-signed-rank]

a non-parametric rank test to compare two paired samples, whether values in one are bigger than in the other. This test is NOT the same as the sign test.

Differences between the two variables are ranked. The null hypothesis is that the mean of these ranks is zero, which implies that the distribution of differences in the population is symmetric about zero. The alternative hypothesis is that it is not so, and thus values of one of the variables tend to be higher. This tag is NOT to be confused with the [sign-test] tag.

481 questions
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Test whether two rank orders differ

I have 20 human subjects doing a task under 2 different difficulty conditions. (So it's a repeated measures design) Each person has a different performance in each of the task difficulty conditions, so I can rank-order them. I want to test whether…
elisa
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Wilcoxon signed rank test – critical value for n>50

I have seen that someone has asked a similar question a few years ago, but unfortunately the answer is not helpful. I am in the process of estimating a Wilcoxon signed rank test with a n=63 by hand. I calculate by hand to really understand all the…
Sophia Back
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Symmetry assumption in Wilcoxon's Signed Rank Test

I'm trying to understand the assumptions in Wilcoxon's Signed Rank Test. From here I understand that "The test is based on signed-rank of observations that are drawn from a symmetric continuous distribution population with unknown median. When…
wrahool
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Which test to use to compare non-normal distributed data sets with a small sample size?

So I have several data sets, but each data set consists of only 7 values. I know some of the data sets are non-normal distributed, so my idea was first to do a Wilcoxon Signed Rank Test. But doing it (in python) it tells me, that my sample size is…
Denver Dang
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What can we say when the Wilcoxon signed-rank paired test shows significance but the means and the medians have different orderings?

In Wilcoxon signed-rank paired test, the hypotheses are $H_0$: difference between the pairs follows a symmetric distribution around zero $H_1$: difference between the pairs does not follow a symmetric distribution around zero So 0 is both the…
Ziyuan
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why wilcoxon signed rank test is better than binomial

Let $\vec{x}$ be 100 iid random varibles such that $x_i \sim \mathcal {N}(0,1)$ Let $\vec{y}$ be 100 iid random varibles such that $y_i \sim \mathcal {N}(1,1)$ For this example, the signed-rank test gives the p-value $\approx 10^{-8}$ I would like…
Aleksejs Fomins
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Wilcoxon ranksum test gives a p=0

I want to see if an app was effective in changing the behaviour of a group. Data were taken at baseline and after intervention on the same group. Since distribution doesn't follow normality I applied Wilcoxon signed-rank test and I get as a result a…
Andrea
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Clarification on the Wilcoxon Signed Rank Test Procedure

The Wilcoxon Signed Rank Test is immensely intuitive and cool in its simplicity. So much so that any questions seem out of place. However,... I have found different procedures being detailed regarding the actual computation of the test statistic.…
Antoni Parellada
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Wilcoxon one-tailed signed rank test

It's regarding a one-tailed Wilcoxon sign test. I am comparing (fictional) ratings of liking before and after an apple is peeled. The design is complicated. I will do my best to explain. There are 9 apples. Participants are asked to rate how much…
shabnam
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Zero differences and Wilcoxon signed rank test

I am wondering if the Wilcoxon signed rank test is an appropriate test for my data, that does not follow a normal distribution. I have 150 datasheets of numbers of drugs measured at two points in time. 40 negative ranks (reduction in number of…
StefanM
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Why is the null hypothesis for Wilcoxon test not rejected if the sample size is 5?

If I perform a simulation for the one-sample Wilcoxon test (2-sided) for samples of size 5 (1000 times), the null hypothesis could not be rejected. Why? I know the probability of the test statistic being equal to zero is 1/32= 0.03, which less than…
Statistical scientist
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Wilcoxon Test with n=4 per group not significant, why?

I have the price per bottle Preis Normal of a certain drink, the difference is the number in each packaging. the Magnum is double the size of the normal bottle, so Preis Magnum / 2 should give the same value as Preis Normal, which isn't the case…
MaxT
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Can someone explain to me need symmetrical distribution for Wilcoxon signed rank test?

So I am confused. I understand that Wilcoxon signed rank test does not need to have normal distribution (hence why it is used when your data is non-normally distributed in place of paired samples t-test). What I don't understand though is that the…
user321998
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How to get single sample result wilcox_test in R

I am not a regular R user so I'm struggling a bit on how to get an exact p-value and confidence limits for a single sample using the Wilcoxon Signed-Rank test. wilcox.test does not handle ties so it's automatically defaulting to normal…
Ryan Boch
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Wilcoxon Signed Rank Test yields p = 1? (two-tailed, small sample size, exact p)

I am performing a Wilcoxon signed rank test on my dataset. Because the sample size is quite small I use exact p values (as described here.) Somewhere else I once read that the p values associated to W can be doubled for two-tailed tests. (e.g. n =…
Fabian
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