The Mann-Whitney test is a non-parametric rank test to assess "whether one of two samples of independent observations tends to have larger values than the other" [Wikipedia].

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Mann-Whitney output confusion

In an experiment I exposed each of 4 subject groups to a different condition to observe the impact on dependent variable. Assumptions for parametric tests were violated hence I decided to employ ...
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Why are these differences not significant (Mann-Whitney U test)?

For my academical research, I have generated eight Twitter bots. Each bot is specialized in one subject. I have four subjects and two genders (a bot can be either male or female), and each bot has a ...
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17 views

Comparing capture rates in 2 groups: which test?

I am comparing rate of capture (animal captures per hour) between two years. I'm interested in determining whether there is a difference between rate of capture between the two years. A survey night ...
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24 views

Different sample sizes, skewed data and unequal variances

I am a bit confused regarding best statistical test to use for my data. Here is the details: I did a study to compare two independent groups; 31 patients and 60 healthy controls. I have around 50 ...
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1answer
26 views

Can I conclude whether these two populations are different?

I'm trying to determine whether my patient population differ from my control population in regards to number of children fathered per individual. The tables show the frequency of amount of children ...
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16 views

With or without outlier and/or parametric vs non-paramteric

I'm comparing two group on the number or movie seen in the last mont (30 people in each group). Spss say that there 4 outlier but when I'm lookin with the z score I only find 1. If I do a t-test ...
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47 views

Mann-Whitney U suitable for my analysis procedure?

I examine the relation of written language of investors and investment performance of investors. N=52 Dep. variable -> investment success; binary (1/0) (Acquisition/no Acquisition) (N = 28/22) ...
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203 views

Does Bonferroni apply to inference from parametric and non-parametric models?

I have run 6 independent-samples t-tests, and 4 Mann Whitney U tests. When applying Bonferroni correction, does it apply across all 10 tests? My hypotheses are that there will be 4 significant ...
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19 views

determine which of the populations is “larger” with Wilcoxon/MannWhitney test

when using Wilcoxon test in Python - I get that one population is significantly different (greater) than the other. Where in the output do I get which population is actually the "larger" one? would ...
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Is there any test, like Mann Whitney U test or Kruskal Wallis test, that allows me to include a categorical covariate (like an ANCOVA)?

Here is my question: I want to know if there is a test that allow me to do an nonparametric ANCOVA. Let me explain: I am looking for a Mann-Whitney-U and a Kruskal-Wallis, but I want to include a ...
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1answer
22 views

Should I use Wilcoxon Signed Rank or Mann Whitney U in this question?

Stats newbie here currently trying to teach myself some stats topics. When testing for evidence that mean earnings per share were higher in 1988, should I use Wilcoxon Signed Rank since the samples ...
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17 views

Compare two values for same measurement between two groups

I have a set of data, that I need to compare. Set consists of two measurements from same individual (right and left arm and legs for example)k like below: ' values_1right - 1, 4, 5, 7; values_1left ...
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Is Mann Whitney U test appropriate for samples of really different sizes and distribution?

A Mann-Whitney U test on two samples of different sizes (Group A: 170,000) Vs. (Group B: 200), different distribution shape (as per Kolmogorov-Smirnov Tests ks.test ...
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15 views

Most appropriate test for count data

So I've performed an experiment whereby I had 12 1km transects. 6 of these were along rivers running through agricultural land and 6 through woodland. These were arranged in pairs so that each agri ...
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25 views

Paired or non-paired data? comparing two sets of scores from same individuals

I have data from four companies, W, X, Y and Z. For each company, three groups of 5 individuals (15 individuals total) take part in a test. Every individual takes two tests, test A and test B, with A ...
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1answer
51 views

Relationship between AUC and U Mann-Whitney statistic

Recently I learned about the relationship between Area Under (ROC) Curve and $U$ statistic of the Wilcoxon-Mann-Whitney test. It is supposed to follow the following rule (got it from this nice post on ...
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1answer
26 views

Mann-Whitney-U-Test as a replacement for Chow-Test?

The Chow-Test tests if there is a significant difference between a pair of regression equations under the null hypothesis the two models are equivalent. My idea is to use the Mann-Whitney-U-Test to ...
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52 views

Change point detection test using Pettitt-Mann-Whitney test?

I am getting two change point with same p-value (or 90.27% probability) in an interval of two years i.e., 1955 and 1958. Here the trend is increasing from 1901-1955 and 1958-2015. How it could be ...
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33 views

Mann-Whitney test W statistics

Below is Mann-Whitney test result from Minitab. At the end of result, there is no p-value but "Cannot reject since W is < 363.0". What does it mean? I cannot ...
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21 views

Wilcoxon Rank-Sum vs Signed Rank for paired

I'm working with a dataset that contains paired samples (but some samples are missing their pair) and I want to check for an association between a binary variable and a bunch of numeric variables. ...
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1answer
116 views

To use a two-sample t-test or to use a Mann-Whitney U-test on spatial data?

I have obtained some mean summer temperature records (June 1st- September 30th) for all years within the 1930s (1930-1939) and I have obtained summer temperature records for all years within the ...
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177 views

Statistical tests for uneven groups

We performed an experiment (usability testing), which had two independent samples, one group with 5 participants and the other with 24. Based on the analysis of the distribution of the data ...
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1answer
58 views

One-sample test, small sample size (n=3), non-normal data

I have approximately 5,000 variables, each with 3 data points. These numbers are ratios, i.e. bounded at 0 and generally non-normal. I'm interested in testing whether the mean of each of the 5,000 ...
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47 views

Estimating sample size for Mann Whitney U test

I'm trying to estimate the required sample size for 80% power in an A/B testing, comparing user ratings with the Mann Whitney U test, and I'm having a problem with the power estimation. I'm using ...
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12 views

Comparing two groups with multiple samples for each subject

Assume that you have multiple patients and control subjects. For each patient and control subject, you take two blood sample and count the number of bacteria you see in each sample. In the end, you ...
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53 views

How to compute difference in location computed in Mann-Whitney-test?

I would like to reproduce the results of the Wilcoxon-Mann-Whitney-test in R wilcox.test(x,y,paired=FALSE, conf.int=TRUE. I succeed to get the W-value but didn't ...
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Can the Mann-Whitney U test be used for related data?

I am comparing the annual profit margins of a set of 15 restaurants before and after they gained a "Michelin Star". I have multiple non-uniform numbers of profit margins for each restaurant before ...
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21 views

Using Mann-Whitney U instead of T-test in large sample

For my dissertation, I am examining racial differences in perceived choice and control and home and community-based services (HCBS) use in frail elders (n=659) who have moved from a nursing home into ...
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13 views

Non-normal, related but non-paired data, test for significant difference

i am comparing the profit margins for restaurants prior and post gaining a michelin star. I have all the profit margins for each restaurant up to 2-5 years prior and post. I want to compare all of ...
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2answers
57 views

How do I get which experiment is doing better using the Mann-Whitney U Test?

The material I got only described how to test if there is difference (null hypothesis: H0 = H1). However, what I want to test is if the test version is doing better than control: null hypothesis: H0 ...
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1answer
52 views

Is the Mann-Whitney U Test appropriate for assessing the busiest day of the week?

We have ten years of data where the average overall reveals that Monday is the busiest with the most visits to the hospital. We would like to provide a p-value to support that observation. Given ...
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81 views

FDR correction of Mann–Whitney U test

I have applied the limma moderated t-test on some proteomics data, on the label free quantitation values of proteins between control and exposed groups (2 samples each). Limma outputs p-values and the ...
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48 views

Am I using the Mann-Whitney U test correctly?

I have two samples of online articles of different forms (one sample contains posts without infographics, and the other with infographics). Sample 1 (w/o infographics): n = 4993 Sample 2 (with ...
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36 views

How is the Mann-Whitney U statistic calculated in SPSS?

I get different results using NPTESTS and NPAR TESTS in SPSS for the U-statistic. Can someone please tell me which formula is used for these two procedures, respectively. It looks like NPAR TESTS ...
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48 views

Any alternatives to Kruskal-Wallis and post-hoc tests?

I have non-parametric data comparing people's sense of community scores who use different modes of transport to travel I want to see if there are significant differences between the three modes of ...
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2answers
98 views

How to interpret Mann-Whitney's statistical significance if median is equal?

Testing the difference between the observations of two groups by using Mann-Whitney Test has given the following output (from minitab): ...
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38 views

Can increasing the significance level help to avoid detecting minor differences in large datasets?

In the accepted answer of THIS question, it is stated that "With such large sample sizes both tests will have high power to detect minor differences". On the other hand, a voted up comment in THIS ...
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33 views

Can I validate results after statistical hypothesis testing?

I have data from one clinical test for 450 patients. Depending upon my objective, I divided data into 7 different categories to compare two groups, in each category (inherited from parents and not ...
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34 views

Multiple comparisons when preforming a t-test and Mann-Whitney U test

I have 90 proteins(column) and about 170 samples(rows) with data. The data describes protein levels for 90 different proteins. Every samples is also in a group, A and B. I would like to preform a ...
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1answer
39 views

Help determining a statistical test to use

I have a data set that has the ages, weights and heights for 444 Olympic athletes. I'm wanting to compare each of these to whether or not that athlete won a medal and see what the correlation is and ...
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11 views

What Would be the Best Statistical Test?

I want to see if the fiscal year end densities for public and private companies come from different distributions. The null being two samples come from the same population and the alternative being ...
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95 views

Mann-Whitney (U) Test at N>20

I am a high school Psychology student. I just performed a study where two separate groups of sizes 26 and 28 took the same test under different conditions. For the data analysis my professor has ...
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15 views

Why I receive a n/a sign with a Wilcoxon rank-sum test calcualtor? [closed]

I was wondering why I receive a n/a sign with a Wilcoxon rank-sum test calcualtor. I used a calculator find from internet but I cannot understand the n/a interpretation. Here is a screenshot: Does ...
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12 views

Non-parametric tests for different measurement scales?

Not sure if I'm expressing this correctly. I've done a survey of my statistics class. I've collected the following information Mathematical knowledge before taking course, coded as 1 (basic), 2 ...
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28 views

Minimum sample for non parametric test?

Exactly how many sample to be minimum size for non parametric test? Right now i have 3 data with really2 small sample size 1. 5 pairs for wilcoxon signed rank test (pretest and postest in 1 place) 2. ...
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44 views

Direction of Mann-Whitney significance test result

I have conducted a Mann-Whitney $U$ test to identify if there is a significant difference in ranking (on Likert scale) of a dependent variable between two groups of people: e.g. those who have <5 ...
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1answer
54 views

Is Mann-Whitney U test valid for unequal non-normal dataset? If not, what is?

Summary: I have a population of people split randomly into seven distinct cohorts, amongst whom events occur each month with varying frequency. We have made the same environmental change across all ...
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1answer
92 views

similarities between t-test ,welch test and mann whitney test

I am newbie to statistics field. I find it is quite hard to understand this few tests even though they are common tools for testing hypothesis. As i am referring this paper actually "should we always ...
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51 views

is mann whitney an alternative to t-test?

can i compare both of them ? As i may change the sample size , variance and also skew the distribution. However,some researcher claimed that comparing both of them couldnt make sense as it is just ...
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236 views

How to validate k-fold cross validation results for classifiers?

I've applied 6 classifiers on my data set using 5-fold CV to calculate average AUC for each model. What method do you suggest me to determine which model has the highest AUC? I've heard of t-test and ...