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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961 views

Change over time between two groups and within groups - Mann Whitney or Kruskal Wallis?

I have two groups (Control and Disease) and for each group a variable y is measured at three time points (0H, 24H, 48H). I want to know two things: Does y change between Control and Disease at each ...
0 votes
1 answer
88 views

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 ...
1 vote
1 answer
1k views

Alternative Effect Size for Mann-Whitney-U to Cliff's Delta

I am working with two variables that are not normally distributed with a large sample size in each group (n=287521, m=10863). After computing the U statistic and corresponding p-value, I tried to do ...
0 votes
0 answers
21 views

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 ...
0 votes
1 answer
663 views

Pair-wise Mann-Whitney U vs. ANOVA

I'm having trouble interpreting the results of comparing 4 sequences. All are fairly similar (in terms of mean) and I want to figure out if one can say that they that their difference in mean is ...
4 votes
2 answers
464 views

Is Mann Whitney U the right statistical test for this analysis?

I am studying the spatial interactions between coral at a specific reef. I have the abundances of each coral species at each site we studied. I also have already run statistical tests and basically ...
0 votes
0 answers
23 views

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 ...
2 votes
1 answer
73 views

Can I calculate ROC AUC from Mann Whitney U tests when I am comparing unequal sample sizes?

I know I am able to calculate Mann Whitney U tests when comparing 2 samples unequal inside but I am wondering if I am able to carry this same principle when calculating ROC AUC via the formula: AUC = ...
8 votes
1 answer
12k views

Differences between Dwass-Steel-Critchlow-Fligner and Mann-Whitney U-test for a post-hoc pairwise analysis

If you have one control and four groups of patients with a non-normal small sample size, there are differences in these tests for a post-hoc analysis after Kruskal-Wallis?
0 votes
1 answer
33 views

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. ...
3 votes
1 answer
78 views

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 ...
1 vote
1 answer
25 views

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 ...
137 votes
8 answers
114k views

How to choose between t-test or non-parametric test e.g. Wilcoxon in small samples

Certain hypotheses can be tested using Student's t-test (maybe using Welch's correction for unequal variances in the two-sample case), or by a non-parametric test like the Wilcoxon paired signed rank ...
2 votes
1 answer
87 views

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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0 answers
14 views

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 ...
2 votes
0 answers
30 views

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
0 answers
13 views

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 ...
3 votes
1 answer
329 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 ...
0 votes
0 answers
24 views

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 ...
0 votes
0 answers
15 views

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 - ...
1 vote
1 answer
70 views

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 ...
5 votes
2 answers
2k views

Can the Wilcoxon rank sum test give a different result to the Kolmogorov-Smirnov test result?

Let's say I have two data sets (in R, say); $x_1, x_2,..., x_n$ and $y_1, y_2,..., y_n$. The Wilcoxon rank sum test rejects, indicating that the "X" population distribution differs from that for "Y". ...
6 votes
1 answer
1k 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 ...
0 votes
1 answer
36 views

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 ...
3 votes
1 answer
277 views

Comparison of different statistical tests on different amount of biological replicates

I am testing differentially expressed genes using different statistical tests on different amount of biological replicates (Wilcoxon test, t-test and negative binomial test). Figure below is what I ...
25 votes
2 answers
17k views

Non-parametric test if two samples are drawn from the same distribution

I would like to test the hypothesis that two samples are drawn from the same population, without making any assumptions about the distributions of the samples or the population. How should I do this? ...
0 votes
0 answers
13 views

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 ...
0 votes
1 answer
2k views

Non-Parametric Test controlling for third variable

There are two laboratories measuring identical samples. One of the lab's data is non-normal, therefore I am looking for a non-parametric test. After comparing overall differences in the dependent ...
6 votes
1 answer
3k views

Different ways of performing the Wilcoxon rank sum test and the interpretation of the resulting W-statistic

What is the practical difference between wilcox.test(x,y, paired=F) and wilcox.test(x~y, paired=F) (i.e. using comma vs. tilde ...
0 votes
0 answers
17 views

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 ...
0 votes
0 answers
31 views

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 ...
0 votes
0 answers
14 views

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 ...
1 vote
1 answer
392 views

Comparing means with three data points

Which statistics would be ideal for comparing two groups with three unpaired data points in each group? With just three data points, I suppose a t-test would not be ideal.
1 vote
1 answer
855 views

Ranked t-test or Mann-Whitney U test for commerical A/B testing

Please help me understand how this blog post relates to this experiment. Here I try to reproduce quite old paper from Zimmerman about Mann-Whitney U test and ranked t-test (and also plain t-test) ...
0 votes
0 answers
31 views

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 ...
0 votes
1 answer
1k views

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 ...
0 votes
0 answers
20 views

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/...
1 vote
1 answer
154 views

Why is the Wilcoxon test not significant for this data?

The 2 data.frame count values look quite significantly different to me, so I'm wondering why the output of the Wilcoxon test is not "significant." Here is ...
1 vote
0 answers
50 views

Between Subjects Likert Analysis -- Treat as Ordinal or Continuous for Stats Test?

I have 4 groups in a between subjects design answering likert scale questions. I am wondering how to analyse the data. There are 20 questions for each user in each group of 30 (so 120 people all ...
0 votes
1 answer
89 views

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 ...
0 votes
0 answers
32 views

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
1 answer
321 views

Mann-Whitney Normal Approximation process help

Let $X_{1}, X_{2}, ..., X_{n}$ is i.i.d sample from $X$ and $Y_{1}, Y_{2}, ..., Y_{m}$ is i.i.d sample from $Y$. And both samples are independent each other. Trying Mann-Whitney U-test then, $U =$ $\...
0 votes
0 answers
25 views

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 ...
1 vote
0 answers
45 views

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 ...
-1 votes
1 answer
94 views

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 ...
0 votes
0 answers
20 views

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 ...
7 votes
3 answers
19k views

Always use Welch-t test (unequal variances t-test) instead of Student-t or Mann-Whitney test?

I want to do an AB test to check if one version does significantly increase revenue. Generically speaking I want to test whether the central tendency (mean) of 2 groups are different from each other ...
0 votes
0 answers
45 views

Wilcoxon test - which is difference and applicability of signed-rank and rank-sum?

I don't have a strong background in statistics, I am reading two papers which mention Wilcoxon tests, signed-rank and rank-sum, and they are applied on two different situations. I found a bit ...
0 votes
0 answers
11 views

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 ...
3 votes
1 answer
7k views

Mann Whitney or two tailed t-test

I am new to statistics and am in need of some help. I am running a study where I am providing two groups with surveys to test for their perceptions using a Likert Scale. One group I'm testing prior to ...

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