# Questions tagged [wilcoxon-mann-whitney-test]

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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### Is it possible to combine two u-tests to get strictly greater than alternative?

When applying the u-test we can have the null hypotheses $a<b$, $a=b$, and $a>b$ which leads to the alternative hypotheses $a\geq b$, $a\neq b$, and $a \leq b$, respectively (at least using ...
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### What test to use for comparison of multiple groups based on multiple dependent variables?

If I have 3 groups X, Y, Z and two dependent variables of interest a, b, what is the appropriate test to compare whether group Y is more similar to X or Z based on both a, b simultaneous?
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### How to validate the effect of the type of Task on participants' performance using count data

We conducted a user testing with two groups of participants (Group_A, Group_B). Group_A performed Task_A (a writing) under Condition_A. Group_B performed Task_B (a writing) under Condition_B. Group_A ...
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### Type of Hypothesis Test Question

I’m trying to answer if males or females rate “The Office” higher or not. Initially, I was planning on using an independent samples t-test, but I wasn’t sure if that was appropriate since nearly three ...
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### Compare whether one group are significantly closer to real observations than other

I have two groups consisting of non-parametric estimated data of a phenomenon. I want to compare these two groups of estimations with a third group of real observations of the same phenomena. ...
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### Mann Whitney U or Wilcoxon Sign Rank test?

I have been collecting data where participants have been allocated to one of three different conditions and had to answer some questions. The data looked like this: ...
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### Mann Whitney Assumption of equal distribution not met

The null hypothesis assumes no difference between groups .Testing Data normality revealed non non-normal distribution so I opted for the Mann Whitney , but testing for Levene Homogeneity of Variance ...
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1 vote
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### Welch's t test vs Mann-Whitney for very unequal groups

I have two vastly unequal groups (n1=18 and n2=400), and want to test mean differences between the groups for some 700 parameters (more specifically, RNA expression levels for 700 genes). While I ...
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### Test two samples with correlated observations within sample

I have repeated observations from individuals that have been randomly assigned to either Group 1 or Group 2. In detail, 64 subjects were randomly assigned to one of the two groups and performed a task ...
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### A\B test and sample size calculate for time data

I am doing a statistical test (analysis) for the following case: As part of a product aimed at improving the quality and speed of code writing for developers, we have implemented a new feature that ...
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### Detecting Mean differences on streaming data

Im taking online measurements on highly skewed real valued data of two possibly unrelated distributions. The precision is low, which means small values tend to come in duplicates, while large values ...
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### How can I explain signifcant combined groups in Mann Whitney U but no individual effects in Kruskal Wallis?

I am struggling to get my head around the concepts of my tests and how to explain them. Unfortunately we didn't recieve much in depth teaching about it on my course. I have 4 variables, one is a ...
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### SIgnificant P-Value with overlapping boxplots

I'm confused about some of the results I got after plotting my data. I have a data set that includes tests scores and a binary group assignment of either polypharmacy or non-polypharmacy. the scores ...
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1 vote
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### Clarification: Mann-Whitney-U test vs unpaired-T test

If I have two patient groups (disease+ vs disease-) and I want to compare both groups in terms of their BMI. There are n = 30 in the disease+ group while only n = 18 in the non-disease group. As far ...
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### Critical value of U for Mann Whitney U test for very large sample size of data

I am new to this and would like to confirm my hypothesis testing. I have right skewed data with no ties in the ranking. N1= 56765 and N2 = 56895, U = 1,583,736,025. Now I am trying to find whether to ...
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### Can I use a Mann-Whitney U test to compare 2 small groups, with unequal amounts of data, non-normal distributions, and unequal variance?

I want to compare data between 2 independent groups to determine whether there is a significant difference between the groups. 1 group has 8 data points, and the other has 9. Separately, I would like ...
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### What sort of statistical test should I use to determine significance between independent groups in my (kind of unprecedented and strange) study?

I have designed a study where I am collecting price data from a particular niche of businesses in my state. Some of these businesses are owned by a conglomerate, and others are not. I want to know ...
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### How do I determine whether there is a significant difference between two sets of price data?

I am conducting a study where I am collecting prices from two groups of funeral homes in a particular state: in the first group, the homes I collected prices from are owned by families, and in the ...
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### What statistical test of significance should I use when comparing two small, unequal groups of non-normal distribution?

I am trying to analyze quantitative data between two independent groups. One group has 8 data points, and the other has 9. I used a Shapiro-Wilk test for each of the groups to determine normality, and ...
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### What does a wilcox.test W result of 0 mean in R? [duplicate]

I am running wilcoxon/mann-whiney tests in R using this as input. I am using this instead of a t-test as the data was didn't fit the assumptions of a parametric model. ...
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### What kind of significance tests can I apply on before/after data that involves proportions?

I am trying to determine whether there is statistical significance from two groups of data. I have the data in terms of counts and proportions or percentages. There are two columns which show the ...
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### What's the correct tool to compare means between very small groups?

I'm not really used to VERY small samples, so I'm wondering what to do in the following situation: I have 3 groups, A, B and C. Each of them consists of 3 observations. I want to test whether there is ...
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1 vote
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### Why choose smaller U in Mann-Whitney U test?

When performing a Mann-Whitney U hypothesis test between two samples of different sizes, why always use the lower $U$ value to compare to the critical value? Is this rule followed regardless of ...
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### Unclear as to purpose of K-S test & U test in this study

I'm currently looking at this study's statistical measures: https://www.sciencedirect.com/science/article/pii/S0191886920302531?via%3Dihub Somewhere in the paper I noticed this: I have some questions ...
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### Multiplicity correction after performing non-parametric tests

This is a theoretical question. I am wondering if multiplicity correction is applicable in the case of non-parametric tests. I have performed some Mann-Whitney U rank test on two independent samples ...
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### What test to use to see whether the number of patients in the two hospitals is the same?

The number of patients in a given age range attending the Accident and Emergency Services of two hospitals P and Q on independent days are as follows. The days for the two hospitals are independent of ...
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### How to compare responses of two independent samples of a Likert scale using IRT?

I want to acknowledge that I am very beginner in this topic of Likert scales and Item Response Theory. So, I have responses from two groups to a questionary with 8 items which ordinal responses can ...
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### Compare value of two time trends - which statistical test use?

I have a three time trends: -time trend representing values before 2020 ("prepandemic") -forecasted time trend based on prepandemic trend (I used TBATS model) -actual observed values I want ...
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### Extension of the relationship between ROCAUC/c-index and Wilcoxon-Mann-Whitney U

There is a relationship between ROCAUC and the Wilcoxon Mann-Whitney U test of the probability predictions of the two groups. If our $y$ variable has more than two classes, can we extend this to a ...
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### Can I use Mann–Whitney U test on clustered data as method to show that the clustering model is good or bad?

I have some data with about 10 features, values for most of which are discrete in nature. I have done clustering analysis on the data and have used various clustering algorithms such as Kmeans, ...
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### Kruskal Wallis test or ANOVA for G-mean?

I currently working on the data (4 groups), which requires the evaluation in Geometric means. I transform the data into logarithms (which is non-normal distributed), then I wonder whether to use ANOVA ...
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### Mann-Whitney U test on "histogram-compressed" data?

I want to perform a very large number of Mann-Whitney U-tests between many groups from data that I will get in from a database. I would prefer to use a pre-implemented version of this test. I think ...
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### Valid statistical test for difference in age between two time points (for a cohort with additional membership)

The question at hand is whether the membership for an organisation has 'aged' from 2016 to 2021. 2021 membership is made up of 2016 members who continued to 2021 and new members from 2016 and 2021. ...
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### Pre- and post significance analysis with random samples (independant / unpaired) for discrete (binary) metric

I am conducting an analysis where I want to check if there was a significant difference in CTR (discrete metric) when an element is moved higher in the page. The samples will be different but I have ...
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### Wilcoxon test for independent groups, but with repeated measurements

I need to compare the average amount of money earned by the control group versus the experimental group on a trial level. Each group has 25 subjects. The variable doesn't have a normal distribution, ...
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### Appropriate test for two not-normally-distributed data samples

I have some data comparing training participants who experienced the same training course either face-to-face or virtually (via Zoom). I have two survey items I am comparing. Sample A is for virtual ...
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### Why are the stated facts about using the Mann-Whitney U test for post-hoc testing after a Kruskal-Wallis test a problem?

I've read here on several threads that using Mann-Whitney U for post-hoc tests are an issue because: the ranks that the pair-wise rank sum tests use are not the ranks used by the Kruskal-Wallis test (...
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### Mann Whitney U test criteria for the shape of the data

As far as I know if the assumption for Mann Whitney for similar distribution of shape is not met the test results represent the test of the mean rank instead of median. What does this mean for the ...
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### Actual difference between the statistic results from scipy.stats.ranksums and scipy.stats.mannwhitneyu

So, I have been trying to test if two independent samples come from the distribution, i.e. if they are greater or less than one another. Eventually I found out the Mann Whitney U Test is the ...
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### T-Test or Wilcoxon Rank Sum Test?

So, for an experiment I analyzed behavioral data of two different treatment groups with $n = 30$ for each of two groups, so 60 subjects in total. I used a computational model to analyze the data and ...
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### Can I use a Mann-Whitney U Test with a very small sample?

I want to compare differences between two independent groups (female and male) when dependent variables are continuous. However, my sample size is very small (N=6). I have done a Mann-Whitney U Test ...
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### Concept Clarification: Wilcoxon rank test vs two-samples T-test (UPDATE)

I am currently deciding whether to use the Wilcoxon rank test vs two-samples T-test to assess BMI between two unrelated groups. Using the following code to assess normality ...
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### Mann-Whitney with more than 10 repeated number of measures

I am currently assessing ab test result by using both bootstrap and u-test and both of them show different results. E.g. The effect on GMV could be significant by MW test but not significant in ...
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### Appropriate test to test for difference in mean (Likert scale)

I want to find out whether the mean of a certain variable (rating on a 5-point Likert scale) significantly differs from the midpoint of the scale, i.e. 3. My sample size is 48. I am wondering whether ...
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### Efficient calculation of critical values for Mann-Whitney-Wilcoxon

Most tables of critical values for the Mann-Whitney-Wilcoxon rank sum test statistic, usually known as U, are only calculated for very small samples. Presumably, this is because the test is most ...
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### Using software to apply tests under different perspectives (sets of hypotheses $(H_0, H_1)$)

I have read very useful paper "Wilcoxon-Mann-Whitney or t-test? On assumptions for hypothesis tests and multiple interpretations of decision rules" by Fay and Proschan (2010). This paper ...
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### Wilcoxon Rank Sum Test appropriate?

I'm using Wilcoxon Rank Sum Test on my data and I'm wondering if there is a better alternative to use and eventually what post-hoc I could do on my data. Context: The objective is to find the ...
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### Assumptions of Mann-Whitney test for at least ordinal data

I am reading article by Divine et al. about using Mann-Whitney test for data that is at least ordinal (i.e. it may be discrete with many ties). It says the following (in section 2.3): That is, it (...
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### How can we prove that kruskal wallis test and jonckheere test is equivalent to wilcoxon rank sum test?

How can we prove that kruskal-Wallis test and Jonckheere test is equivalent to Wilcoxon rank sum test when k = 2? And how can we prove that Friedman test and Page test is equivalent to sign test when ...
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