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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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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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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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 ...
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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 ...
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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 ...
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Combined p-value from wilcoxon test result on control experiment - interpreting the null-hypothesis correctly
EDITED
I spotted error in my code, and now results are no more contradictory. But still I keep the question for utility of others and myself in understanding meta-analysis and correctly interpret null-...
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Can I combine the Mann–Whitney U test results for several distributions?
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 ...
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Leave-one-out validation after Wilcoxon rank-sum test
I am comparing 2 groups of sizes 13 and 28, using the Wilcoxon rank-sum test. While I think this method should not be very susceptible to outliers as it relies on ranks, I still want to investigate if ...
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Which test to use for small and unequal samples
I have a sample of stroke patients and I want to find the education effect on their performance in a neuropsychological tool. The total sample is n=19. I have divided the sample into 3 groups ...
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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 ...
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Paired t-test of non-normal data - help please
I have a paired data with n=50. I am using a paired t-test to test the difference in quiz scores before and after an interval. My data for quiz scores after the interval is showing as not normally ...
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Comparing ratings generated by overlapping groups of experts
Consider an experiment where randomly selected experts from a set are asked to attribute Likert-scale ratings to randomly selected objects from two groups A and B. Now, suppose I want to test whether ...
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Wilcoxon test for two groups or post hoc analysis of K-W test when I woud like to compare two groups and observe the difference?
I am working on data analysis. I divided my samples into five different groups (group A-E) by using some variables. and then, because group A can be further reclassified into group A+ and group A- and ...
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Kruskal-Wallis returns only one significant group (out of 4 groups), when significant group is removed and test redone, another group is significant?
I am comparing 4 groups of samples using SPSS. The groups are 4 bathymetry groups (>0m, >-1m, >-2m, >-3m). Within each group are a number of samples n. Each sample has a recorded seagrass ...
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Can I do the Mann-Whitney test with different sample sizes 18 and 32?
Can a Mann-Whitney test be done on different sample sizes, one sample about 18 and the other about 32? The problem is looking at the difference in views of tourists and locals about the environmental ...
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Is there an optimality result for the two-sample Wilcoxon-Mann-Whitney test?
Is there any mathematical result that states that the Wilcoxon-Mann-Whitney (WMW) test is optimal in some sense, for a specific testing problem that is a subproblem of the general problem the WMW test ...
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Why is the pseudomedian better than the median in a Wilcoxon test?
The wilcox.test function in R calculates the pseudomedian and a confidence interval when conf.int=TRUE.
In this question, ...
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Best way to compare group characteristics
I have a dataset (say N=200) of which a subset (N=150) have undergone a certain assay. I want to be able to say that the subgroup N=150 is not significantly different from the entire population (N=...
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Testing if two distributions are the same with Mann–Whitney U test given equal median
Given two independent variables $X$ and $Y$, I want to test if they follow the same distribution.
$H_0: F_X(.)=F_Y(.)$
$H_1: F_X(.)\neq F_Y(.)$
I do not want to test if their medians are the same.
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Mann-Whitney U test returning small p value
I have two vectors, A and B which I want to compare using the MWU test. Both vectors have the size of 995 with A having a mean and standard deviation of 10.50050 and 2.82287, respectively. The mean ...
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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 = ...
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Likert Scale - Statistical Analysis?
I have conducted a very large survey (n>10,000). I asked all participants a series of demographic questions (gender, ethnicity, educational background etc - all categorical). I then asked all ...
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checking normality for longitudinal data
From an experiment where we recorded performances before and after medication, I have gathered data for two groups of patients (Disease A and Disease B) and now I wish to examine if there are any ...
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TTest for discrete data with a pareto distribution
I want to compare two sets of discrete data (0 to infinite, but realistically around 450) that don't follow a normal distribution but a pareto distribution, so supossedly I cannot use the Student's ...
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How can I combine and get cdf of joint distribution of normal and beta distributions on the same set of data? [duplicate]
In my problem, I have a condition in which I need to compute the joint distribution of two dependent distributions. The first distribution is normal and the second one is beta distribution. How can I ...
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