# 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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### Discrepancies between Mann-Whitney Test and Linear Mixed Model Results in R

I've conducted a four-phase experiment with physiological measures on two groups (Controls vs. Patients). After applying a Mann-Whitney test to examine differences between groups for each dependent ...
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Let's say I have 2 sets of grades from students. Maybe I'm looking at gender differences or some such but the disaggregating factor could be continuous or multinomial. Group A: 3 D's, 5 C's, 13 B's ...
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### Mann Whitney test problem

I have data from 4 populations : A (n=16), B (n=16), C (n=14) and D (n=16). Data from A and B are not normally distributed. Data from C and D are normally distributed. All data passed the Levene's ...
1 vote
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### Adaptive sample size for determining the significance of difference between two non-parametric distributions

I have two non-parametric distributions, A and B, and I would like to determine if they are significantly different (say, by the p-value of a U-test). Normally, I would sample $n=1000$ from ...
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### Doubt on Mann Whitney U test [closed]

I doubt the ranking of 2 values in Mann-Whitney u test? for example, men's and women's social acceptance. If the men's N is small and the female's N is larger, when comes to ranking men have a high ...
1 vote
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### Z score comparison in longitudinal studies

I have a longitudinal study with two time points (before/after), whereas a particular score was standardized across all individuals and time points, and thus provided only in terms of z-scores. (Edit: ...
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### Basic question regarding before and after intervention analysis on groups of different sample size

Apologies for the basic nature of this question. I have collected data before and after an intervention and assessed response to the intervention using a survey. This was a basic survey using a 1-5 ...
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### Analysis of the difference between two groups on multiple outcomes

My question contains a few variations; I apologize for this in advance. I have two groups, and I have four outcome measures. These outcome measures are assessments of pain, function, depression level, ...
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### One sided Wilcoxon test

I want to check whether a training program made an improvement on knowledge level on participants. I applied a test before and after the training to the same people (this means I have 2-samples, ...
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### Hypothesis Testing - Varying p-value issue in my MWU

I have two machines (A & B) in our production line. A is older, B is very new. Both perform the same tasks, except that machine B is advanced and will perform 1 task less than the no of tasks in ...
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### Nonparametric test (akin to a sign test?) for multiple interacting effects across multiple conditions

Problem I have $K$ sets of conditions (index by $k\in\{1,..,K\}$), and each set has $N_k$ conditions. For example, if $K=2$ and $N_1=N_2=2$, we could call the conditions (A,B) and (C,D). I have ...
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### Statistical significance test for average revenue

I have a dataset with a control group and a group who received a phone call. This is a subscription business, so the aim is to see if the average value of their subscription order increased. The ...
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### p-value correction after wilcoxon/mann-whitney test

I have a set of 56 variables, which are functional connectivity values, for two groups (control_group vs. patient_group) between two phases (pre-phase vs. post-phase). I have a small sample size (9 vs....
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1 vote
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### rank-sum test vs. anova

I have a set of data looks like this: hwid freq code output 101 5150 764 24 101 5170 768 24 101 5190 764 24 102 5150 752 24 102 5170 760 24 ... ... ... 24 The data represents "power level&...
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### How to know if I have enough sample for a small sample t-test to be appropriate?

Say I have 15 or 20 samples each from two samples. The data shows evidence of strong skew. I am considering a two-sample t-test of means, based on the assumption that the sampling distribution of the ...
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### How to combine results from Wilcoxon Rank Sum Test for multiple imputed data sets from proc MI in SAS

Endpoint information: We have seizure count collected for every day and therefore there will be some missing for some days. We got average seizure frequency per 28-day, for an interval. That is, (...
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### nonparametric test for statistical significance for control and treatment

I conducted an experiment called "die-under-the-cup" (DUTC) and now I'm looking to assess the statistical differences between a control group and a treatment group. In the treatment group, ...
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### Do I need to use a factor for the ANOVA? [closed]

The problem: A psychologist is interested in short-term working memory under (1) sleep deprivation, (2) a strong dose of caffeine, (3) following 8 hours sleep. They conduct a between subjects design. ...
1 vote
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### Which statistical test is suitable to compare order statistics of two independent samples?

Say I want to compare two order statistics (say the 2nd largest value or min value) of two samples. Let's not make any distributional assumptions except that the variance is finite? Is something like ...
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### Best test to compare cell population counts across patient groups

Given a data frame structure similar to the following: ...
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1 vote
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### Parametric vs Non-parametric test recommendation

What type of non-parametric test would be suitable for the dataset shown in the image: The sample size is 200 each for both variables. The data value can vary from 0-4 for both variables. The ...
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### Mann-Whitney-Wilcoxon test vs ANOVA for comparison of variable across multiple groups

When comparing a non-normally distributed variable across multiple groups, is it okay to use a Mann-Whitney-Wilcoxon test or is it necessary to use (non-parametric) ANOVA? The ...
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### Correcting p-values when accounting for age and sex in a study where the main objective is to find differences between disease/control

So I analyzed my metabolomics data using Mann Whitney U tests and OPLS-DA. My data is super small, with the control group only having 5 samples and the other groups having 10 and 14 samples ...
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### Mann-Whitney U Test - Interpretation

I have conducted a survey and would like to assess whether men compared to women differ in their attitudes. At a glance, the means differ quite much, which is why I wanted to prove it statistically. ...
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1 vote
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### How to report a difference in means - Demographics

First of all sorry for the question, I'm having a hard time with statistics :) I have conducted a survey for my thesis and am currently analyzing and reporting the results. At the end of my survey, I ...
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### Statistical test for nominal data, multiple variables and within-subject design in R

I have run a study comparing if a cheap ultrasound device (T) is as efficient at determining osteophytes as an expensive device (V). There was four examiners who reviewed each participant (ID) and ...
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### Best method to compare measurement techniques

I am wishing to test the equivalence, or not of two measurement methods. Some background, we have two test instruments (old and new) that measure radiation dose distributions compared to what was ...
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### Relating factors based on conclusions on 2 distinct groups?

I determine that Team A achieves higher customer satisfaction scores than Team B with wilcoxn rank sum test. A customer satisfaction score is calculated from different sized groups of customers, and ...
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### When to use Spearman correlation and when to use Wilcoxon Rank sum test?

I have collected data on 1680 test scores and 1680 participation rates from 7 different courses and 4 different semesters using information from 60 students. I am confused of whether to use a ...
1 vote
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### Which statistical test to use for customer buying subscription for A/B test

I'm running an A/B test, where control has default experience and the test variant has personalised experience. The users I am targeting randomly are lapsed users on a particular subscription and ...
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### What is the best way to compare means across groups if the data is not normally distributed, and sample sizes across groups can vary?

I am quite new to statistical analysis and have what is probably a newbie question. I have a dataset that contains year and state data for two different groups. I am trying to compare the group means ...
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### Comparing subgroup to the overall group, using 3 different tests for nominal and ordinal data

I have a dataset, which has different categories, such as Females vs Males, Race, Ethnicity I also have responses - nominal (yes/no) or ordinal (from 1 to 7). I plan to use 3 tests: Ordinal data - ...
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### Mann-Whitney U-Test critical values for very large samples (in Million

I compared two unequal sized samples, N1 = 108297 and N2 = 72922 using a Mann-Whitney U test. The U is shown to be large such as 7.37 e+8. And p value is < 0.001. I am just wondering that such ...
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### Test(s) for comparing predictor quality for different features?

I applied a predictor to different numeric features from the same group of subjects (n>1000). The features have different ranges. Is it possible in this case to apply a statistical test to make a ...
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### One-tailed Mann-Whitney U-test by hand - which U-stat vs order for treatments on critical values table

I am comparing a certain activity in an animal using a one-tailed Mann-Whitney U-test. I would like to know if the activity increases from treatment A to treatment B. Alternatively, I could look at ...
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### Which post hoc test should I choose - Dunn's Test or Mann-Whitney-Wilcoxon? Analysis of 3 groups of physicochemical data

I am working on a scientific paper comparing physicochemical data from the river and two well rows (3 groups of data) - see example picture: In my study, I want to see if there are statistically ...
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### Analysing pre and post intervention MCQ results for significance- which statistical test to use?

I have ran a teaching course for students. I carried out pre and post session MCQ quizzes to evidence effectiveness of the course, however the marks collected were anonymised (data collected via ...
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### Robustness of Mann Whitney U Test for partially paired data

I'm curious if anyone is aware of a publication that addresses the following matter or could provide a mathematically or reasonable response to the following question: In a pre-post study where ...
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### Non-parametric tests to compare conditionally independent groups

I want to compare two groups using the Mann Whitney U test (also known as the Wilcoxon rank sum test) per this description: https://sphweb.bumc.bu.edu/otlt/mph-modules/bs/bs704_nonparametric/...
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### How to deal with negative values after subtracting the background?

I am working with Luminex data and have a question regarding the treatment of negative values after subtracting the background average. Specifically, I would like to know if these negative values need ...
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### Comparison of KS test and MWW test

I want to compare two data samples which come from continuous distributions. However, the data is highly skewed and t-test is obviously not a choice. As an alternative, I wanted to use the MWW test ...
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### Is it valid to test the divergence of two timeseries using a Mann-Whitney-U test? If not, how can I show doing so will be problematic?

I have two time series that give me a monthly count. One is a reference series that is meant to be used as a control; the other has a 'treatment' or program applied to it mid-way through. Both are ...
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### Which test is the best I can use

I want to find out whether two groups of people (with and without Autism) differ in their interpretation of ironic compliments and ironic criticisms. To this end I did a study with (26?) persons ...
1 vote
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### Fisher exact test for enrichment of subpopulations in single cell data

We have single cell data from 12 control and 12 diseased individuals. The data has been integrated (remove batch effects) and clustered. We would like to know if there are any clusters that are ...
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### How to interpret W value of a wilcoxon test in R

I did a wilcoxon test in R but I don't understand how to interpret the W value and what this means in comparison to another I did result on 2 data sets and the results are: W = 9, p-value = 0.1 ...
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### What test to compare Deprivation Index between two groups

I have two very large independent groups (n=30,000 and 12,000). Each data point is an individual’s UK Deprivation Index decile (the Deprivation Index itself is a ranking from 1 to 32,844 of an area’s ...
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### How can I analyse the influence of a binary variable on a set of pre- and post-survey Likert scale questions?

I've analysed the unpaired survey responses using the Mann-Whitney U test and several questions show a change after treatment at p < 0.05. However I would now like to characterise the influence of ...
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### How to implement multiple comparison correction after Wilcoxon rank-sum test with relativelty small sample sizes and many comparisons

I am comparing 2 groups, performing a total of 180 comparisons. When doing these 180 pair-wise comparisons using the Wilcoxon rank-sum test more than 40 show a significant (p<0.05) difference ...
I need to compare performance of a web-application before and after some code change. We have several pages (call them $P_1$ and $P_2$; in practice there are more than 2), and for each we compare ...