# Questions tagged [wilcoxon-mann-whitney]

The Wilcoxon rank sum test, also known as Mann-Whitney U test, is a non-parametric rank test to assess whether one of two samples has larger values than the other.

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### Mann Whitney U revenue test effect size

I am looking for solutions around non-parametric hypothesis testing on revenue metrics in business settings. Currently I face with difficulties in finding the right way to make a Mann-Whitney U test ...
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### Friedman's Test fails inspite of big differences between the average ranks of algorithms

I performed Friedman's test to validate that a particular algorithm is statistically different from other compared algorithms. For example: I wanted to prove my ...
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### What to do if an exact permutation test is infeasible

For permutation tests, it is often infeasible to enumerate all permutations. There are two approaches to solve this. The first uses a random number of permutations instead of all permutation (this is ...
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### Should I use Mann-Whitney U test, T-test, or something else?

I have a problem where I experimentally want to see if a fall-time for a given a triangular pyramid differ compared to a square pyramid with the same cross-sectional area. Here is the data I have. P3:...
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### Shouldn't higher r values be inversely related with effect size?

I'm conducting a Wilcoxon Rank Sum Test and read that the r from Pearson Correlation is good for determining an effect size. Logically this does not make sense to me as the higher the effect size ...
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### Which test(s) are alternative to Mann-Whitney test for non-parametric continues data when symmetry assumption is violated

From here and here I see that we cannot use Mann-Whitney test if symmetry assumption is violated. Which test(s) can we use instead of Mann-Whitney test for non-parametric continues data if symmetry ...
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### R: Using Wilcoxon rank-sum test to compare categorical data and obtain Cliff's delta effect size

I have the following myData, where the response variable high-rated denotes if an application is high-rated or not, and the ...
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### Comparing 2D data sets using python

Thanks in advance for everyone reading this question. I have to write a program that takes a 2D data set (Force[y axis] versus displacement[x axis] data, if it matters), compare it with around 600 2D ...
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### Can a t-test be used with data from several individuals?

I have turning data for animals in different conditions with comparisons of before and after these conditions, we'll say condA, condB. Each animal has 3 repeats on both conditions, where before a ...
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### Test for different median in two independent groups with repeated measurements

I want to test if the median of a continuous variable (e.g. height) is the same in two independent groups (boys and girls). For each person there are multiple measurements of the continuous variable ...
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### Using Wilcoxon Ranksum text with Equal sample medians [duplicate]

We have two independent samples, with skewed distribution from two different populations x, and y. When we compute the summary ...
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### Variance in a T-test using means/medians

I have turning data for animals in different conditions with comparisons of before and after these conditions, we'll say condA condB. Each animal has 3 repeats on both conditions, where before a ...
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### Calculate the difference in sums (revenue) between two groups in A/B test

Requests for a quote come in completely independently, and our system assigns each to either A or B randomly (50/50% split). B has slightly different logic, that is what we are testing. Quotes ...
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### Is the Wilcoxon two-sample test maximally powered to detect proportional odds alternatives?

We know from the literature that The Wilcoxon-Mann-Whitney two-sample rank sum test is optimal for detecting simple location shifts when comparing two continuous random variables that each have a ...
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### Am I doing it right conducting Mann–Whitney test in scipy?

I have a group of users. I comapre their behaviour before and after certain event. Here are distributions of the metric before and after event. Here are distrubutions ...
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### Wilcoxon-Mann-Whitney test for mean difference under a location shift assumption

If we make an assumption that the difference in the two groups is simply a shift in location, we can say that the test is a test of the difference in medians. However, if the groups have the same ...
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### Is the Wilcoxon rank-sum test a nonparametric alternative to the two sample t-test? Null hypotheses are different

https://www.stat.auckland.ac.nz/~wild/ChanceEnc/Ch10.wilcoxon.pdf says "The Wilcoxon rank-sum test is a nonparametric alternative to the two sample t-test which is based solely on the order in which ...
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### Wilcoxon p-value correction for extremely small samples

I have performed thousands of Wilcoxon test. Unfortunately, for some of the tests size of one of the groups was equal to 1 or 2. ...
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### Wilcox.test for testing count based data in R studio large W

I'm doing a textmining project about a videogame review dataset. I divided de reviews into a positive (reviewgrade > 8) and negative (reviewgrade < 3) and want to draw conclusions based on the ...
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### How to interpret a p value in a Mann Whitney U [duplicate]

Question: Is there a difference between males and females’ ratings of their supervisors’ family supportive behaviors? If we observe the ranks, there is a difference between the mean ranks reported by ...
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### Hypothesis testing on two large, non-normal samples [closed]

I want to compare two large independent groups of integers (each group has 1000+ samples). Both groups are positively skewed. For instance, one group has this distribution: ...
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### Use of the Wilcoxon rank-sum test on two samples where the elements of one sample make up some of the elements of the other? [closed]

I have two samples to compare and I want to determine if they are statistically similar or different. Both are measurements of the same property on the same material. Lets say X contains 25 elements ...
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### Understanding statistical test to use: T-Test vs. Wilcoxon Signed Rank vs. Wilcoxon Ranked Sum — for Visual Analog Scales in paired sample

If I were to give out a survey with questions based on a visual-analog scale, and I want to compare the results for each of these, which statistical test is generally the most appropriate? If for ...
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### Wilcoxon rank sum test variance with ties

When we have ties in our data set when we are using Wilcoxon rank sum test, then we need to take averages of the ranks. If we had no ties, then variance and standard deviation were easy to calculate ...
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### Is “contract statistics” a thing? If not, why not? [closed]

This question is motivated by a ton of prior questions of the form: When can I use [insert statistical technique]? In "contract programming", one cannot call a function without satisfying its ...
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### Statistical tests for count data with many zeros

I have to compare three groups (each group is a customer to a subscription box company). Group A received treatment A. Group B received treatment B. Group C received no treatment. We count the ...
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### How to interpret ggbetweenstats results from ggstatsplot?

I have data which is not normally distributed. In my data there is 2 groups: First: there is around 30000 genes with the counts of EQTLs per that gene, labeled as All Genes Second: there is 103 genes (...
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### Eta-squared from Kruskal-Wallis in R

Is it possible to calculate Eta-squared from Kruskal-Wallis test results? I know how to do it by hand for the ANOVA or Mann-Whitney using the Z-statistics, but i must use the KW test for my current ...
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### What test is the most appropriate in this design with multiple variables?

I have a test design in which I have 1 base condition and around 14 test conditions. Each of those 15 conditions has a total of 15 observation points (so equal sample size). The base condition ...
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### Mann-Whitney U & Wilcoxon W [duplicate]

I ran the Mann-Whitney in SPSS. In addition to the U, the output generated the Wilcoxon W and the Z score. Why would the W and Z be present in the output? I cannot explain them being present. Also, ...
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### 2-sample t-test VS Mann-Whitney test - one group is not normally distributed

I'm comparing two groups of data. One group has a sample size of 30, and the other a sample size of 45. The second group is not normally distributed, and thus this violates the normality assumption. ...
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### In scipy why stats.kruskal can work with two populations?

Krustall-wallis testing should be working only at least with 3 populations.But here, it seems to accept 2. Krustall-wallis extends the Mann–Whitney U test, which is used for comparing only two groups....
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### What statistical test should I perform for the data who comes from more than one population? [closed]

I want to check the chosen property (for example volume, density etc.) between data of experiment 1 and experiment 2, whether the difference of property between the experiment is significant or not? ...
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### Testing approach Chi Square vs Mann Whitney

I am looking to understand the best approach to determine if students in one school performed better on a quiz than another. In this scenario the quiz has five questions and only whole points are ...
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### Example of rejected alternative hypothesis of a Wilcoxon rank sum test?

I've recently looked into the Wilcoxon Rank Sum test for comparing groups of continuous values. In particular I've been using R's wilcox.test() function for this ...
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### about paired or unpaired t.test or wilcox.test in R

Please advise on the use of PAIRED or UNPAIRED T.TEST or WILCOXON TEST (wilcox.test) in R: Let's say we have 2 samples: -- CONTROL : where we measure the ...
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### Reconciling seemingly different null hypotheses for Mann-Whitney test

The Mann-Whitney test ( Rank sum, Wilcoxon-Mann-Whitney ) is according to some authors testing H0: the populations from which the 2 samples were drawn are identical in every respect e.g. see Hoel ...
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### Comparing mean rates between two groups

I'm not sure if I'm doing this correctly so please let me know what you would change. I have data that looks like this ...
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### Comparing sensor data across multiple experiments

I have some questions about doing statistics on a series of sensor measurements. I have 12 series of data of sensor measurements (a force sensor, measuring at 10 Hz for 30 minutes). Each series ...
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### Power difference between t-test and chi-squared test on the same data

Say I have two groups of patients and like to test the association between this grouping and another pathological feature on these patients. Given that the pathological features is nearly continous. I ...
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### What is exactly the non-normality requisite for nonparametric tests? [duplicate]

As the title says, what is exactly what is being tested before deciding to use a non-parametric alternative test (as Kruskal-Wallis for ANOVA, or Mann-Whitney's U for student's t)? Most sources are ...
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### If Mann-Whitney U is a median test? Then what the heck is “unpaired pairwise median”?

Header: I am really sorry for the confusing title. I am going to edit it so it fits the responses I get based on Mann Whitney U. So I had this exact question on stack overflow about is the Mann ...
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### Multiple comparisons between two groups (non-parametric)

Update Added more details about the Experimental setup. My experiment comprised two groups, control (N=25) and experimental (N=26). Each participant belonged to one group. Their performance has been ...
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### How do I know if my experiemental is within 95% matching of my simulation?

I have two datasets, one experimental the other a simulation. The problem that I am having is that the experimental only has about 700 obs while the simulation has about 30000 (software generated). It ...
63 views

### Nearly 0 p-value with Welch's t-test and near 1 with Mann Whitney U test

I have carried out some t-tests on various groups in my data set. The response variable is the number of occurrences of an event in a day; for most observations, there are no occurrences, so the ...
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### Statistical Comparison of Algorithms by User Ratings

I have an experimental setting where I compare 3 algorithms on the same dataset(n_sources), through user subjective evaluation of the produced outcomes(each algorithm does a different kind of sound ...
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### Wilcoxon rank-sum test report results when Mdns are the same

I understand that Medians should be reported when writing results of Wilcoxon rank-sum test. For example: "For alcohol users depression levels were significantly lower on Wednesday (Mdn = 7.50) than ...
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### Why Mann-Whitney stat value is different in R and Python?

I'm calculating Mann-Whitney for a two-sided hypothesis and I'm getting different values for the statistic value: in R ...