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# Questions tagged [kruskal-wallis]

The Kruskal-Wallis procedure is a nonparametric equivalent of one way analysis of variance, used for comparing the location of three or more groups; it extends the two sample Mann-Whitney-Wilcoxon procedure.

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### Post-hoc tests after Kruskal-Wallis: Dunn's test or Bonferroni corrected Mann-Whitney tests?

I have some non-Gaussian distributed variable and I need to check if there are significant differences between the values of this variable in 5 different groups. I have performed Kruskal-Wallis one-...
42k views

### Difference Between ANOVA and Kruskal-Wallis test

I am learning R and have been experimenting with analysis of variance. I have been running both kruskal.test(depVar ~ indepVar, data=df) and ...
12k views

### Is there an equivalent to Kruskal Wallis one-way test for a two-way model?

If the model does not satisfy ANOVA assumptions (normality in particular), if one-way, Kruskal-Wallis non-parametric test is recommended. But, what if you have multiple factors?
3k views

### Testing the difference of (some) quantile-Q between groups?

For some Y variable, that is divided into 3 groups (X), I wish to compare the groups and for the hypothesis that the 90% quantile is the same between all three groups. What tests can I use? One ...
16k views

### Can Mann-Whitney test be used for post-hoc comparisons after Kruskal-Wallis?

I have a simulation where an animal is placed in a hostile environment and timed to see how long it can survive using some approach to survival. There are three approaches it can use to survive. I ran ...
3k views

### Jonckheere-Terpstra interpretation

I am running the Jonckheere-Terpstra in place of Kruskal-Wallis test, as my factor is in ordinal scale (i.e. groups can be ordered). The Asymptotic significance (2-tailed) is 0.000, so it seems there ...
12k views

### Do we need to report the median or the Mean when using a Kruskal-Wallis test?

I have two groups. There is a significant difference according to the KW test. But do I need to report the mean or median of the groups?
3k views

### Analyzing repeated measures experiment with multiple treatment groups and multiple measures

I am doing a study to evaluate the effect of two dietary supplements on body composition. Literature suggests that Treatment 1 (Dietary Supplement 1) affects body composition with some side effects ...
18k views

### Friedman vs Kruskal-Wallis test

I have read the Wikipedia pages for Friedman's and Kruskal-Wallis' test, but I am not sure which one to use. Are there differences in the assumptions?
4k views

### Kruskal-Wallis test data considerations

I'm about to apply Kruskal-Wallis test (non-parametric ANOVA) on three groups of unequal length. I was taught/advised to apply Krukal-Wallis only if: dependent variable is at least at ordinal level ...
24k views

### How to read the results of Dunn's test?

How do I read the results from Dunn's test? Specifically, what do the values in the table below tell me? I have non-parametric data in 4 groups, and I first did a Kruskal-Wallis test to confirm that ...
6k views

### What is the difference between various Kruskal-Wallis post-hoc tests?

[There seem to be a lot of similar questions here, so please point me the right direction if this has already been answered, but I think it's reasonably differentiated.] There are many different ...
3k views

### Kruskal-Wallis test is not significant but some of the Mann-Whitney comparisons are significant

I have a non-normalized dependent variable and an independent variable broken down into 4 groups. As such, I used the Kruskal–Wallis analysis to look for significant differences in the ranks of the ...
6k views

### Bonferroni correction on multiple Kruskal-Wallis tests

My data consists of 3 groups, and 6 variables. The data are not normal so I want to use non-parametric tests to uncover significance. The first thing I wanted to get your opinion on is, is it ...
2k views

### ANOVA / Kruskal-Wallis: one of four groups has different distribution

I'm using Kruskal-Wallis to as a non-parametric ANOVA of a non-normal distribution. My understanding is that it assumes each group of the independent variable has the same shape. As it turns out, ...
322 views

### how to measure the correlation between non-normally distributed numeric variable and nominal variable?

I have two nominal variables and some numeric variables. The first nominal variable is a binary one. I want to measure the correlation between this binary variable and the other numeric variables. ...
9k views

### Power analysis for Kruskal-Wallis or Mann-Whitney U test using R?

Is it possible to perform a power analysis for the Kruskal-Wallis and Mann-Whitney U test? If yes, are there any R packages/functions that perform it?
9k views

### Multiple comparisons in a non-parametric test

I am working with a data set that is non-parametric and has 12 treatments. I performed the Kruskal-Wallis test and got a significant $p$-value, and now I would like to conduct a multiple comparisons ...
4k views

### Nonparametric alternative to ANOVA for testing the difference between several brand preferences

I have collected a data from about 200 customers on their brand preference of 5 international fast food chain shops. Each customer was asked to rank all the 5 brands from highest to lowest (5 for the ...
7k views

### Contradicting p-values for Anova and Kruskal-Wallis on same data: Which is right?

I have a data file with task duration values for three groups, and I want to determine group effect on task duration (tasks were executed by individuals; each group had 7 different individuals; each ...
37k views

### How to report Kruskal-Wallis test?

As part of the analysis of the data collected from a survey, I was carrying out Kruskal-Wallis Tests between some Likert scale questions and demographics such as firm size and job position. I am using ...
2k views

### Kruskal-Wallis and Dunn's

I am trying to interpret the results of some experiments I have run, involving showing participants videos of animated synthesised speech. I ran a mean opinion score test. I made 36 movies in total. ...
37k views

### Which result to choose when Kruskal-Wallis and Mann-Whitney seem to return contradicting results?

I have these groups where the values are responses to a 10-point Likert item: g1 <- c(10,9,10,9,10,8,9) g2 <- c(4,9,4,9,8,8,8) g3 <- c(9,7,9,4,8,9,10) ...
2k views

### Strange result of post-hoc test

I have data for a test on three groups. The measured variable is ratio scaled. The R code is g1a<-c(7, 3, 40) g2a<-c(1,1,2) g3a<-c(0,0,0) Since the ...
722 views

### Kruskal Wallis test with high type 1 error

using this code ...
351 views

### Mann-Whitney U test or Kruskal Wallis test for comparing median of two groups?

I know that Kruskal Wallis test can be used to compare median of two or more groups (e.g. see this link: https://www.statisticshowto.datasciencecentral.com/kruskal-wallis/ ), and that Mann-Whitney U ...
424 views

### Permutation test for two distributions with the same mean but unequal variance

I am using the coin package in R. For two distributions with the same mean but different variance, the test is unable to reject the null hypothesis that the two ...
3k views

### Is ETA a good measure for computing the efect size between an ordinal and a nominal variable?

I have a nominal and an ordinal variable and I would like to look measure the association that is between the two. For now, I have done Chi-square test and non-parametric Kruskall-Wallis Test and I ...
75 views

### Can I use multiple regression on a ranked response variable as a significance test for multiple covariates?

This blog post illustrates the relationship between inference tests on groups (t-test, ANOVA, etc.) and equivalent linear models. It also claims that for reasonable sample size, regression of a ranked ...
194 views

### Estimating Diversity of operon types using HMMs across metagenomes: Mann-Whitney? Kruskal-Wallis? or other?

Question that seems complex but probably isn't. I'm comparing 10 metagenomes (http://en.wikipedia.org/wiki/Metagenomics), that are supposedly unrelated (they are 10 geographically separate locations)...
133 views

### Test statistic for follow up procedure (stepwise step down) of Kruskal Wallis

When conducting a Kruskall Wallis test, it is possible to follow up the procedure with a post hoc test, looking for homogeneous subsets. My question is which statistic is used to perform this ...
1k views

### Adjusting for multiple Kruskal-Wallis tests

I've run 3 different machine learning algorithms on 10 different datasets, generating an accuracy on each one. My hypothesis is that two of the algorithms are consistently better than the third. I've ...
378 views

### Comparing classification results from models selected differently with Kruskal-Wallis

For a seminar at university I'm reviewing a paper that proposes a new feature selection algorithm. The authors also evaluated their algorithm by applying it beside two other feature selection ...
183 views

### Something more powerful than Kruskal-Wallis Test?

I have a sample from a continuous variable under 3 treatments and I want to assess treatment differences in the location of the underlying distributions. One option is to run a non-parametric test ...
712 views

### Where does the number 12 come from and why is it the same 12 in Wilcoxon and Kruskal Wallis?

I see that it has something to do with the variance and one has 12 on the numerator and the other denominator, but why is this the same 12 and how do they become inverse? Equations: Kruskal Wallis:...
1k views

### Same p-value. Is it normal?

I did the following comparisons with a Wilcoxon test on MatLab, and I got the same p-value on both. Is this normal? Is there something wrong? Also, the tests indicate not to reject H0. How to ...
961 views

### Non-normal distribution even with Kruskal-Wallis test

Thanks to anyone who can help! I`ve done a survey with Likert-scale questions with about 1,500 participants. Initial analysis in SPSS showed no outliers (using box-plot) but scores were not normally ...
2k views

### Any other non-parametric alternative to Kruskal-Wallis?

It looks like Kruskal-Wallis is the standard nonparametric test for more than two groups. The problem is that it does not tell which groups are different, except that whether there exists significant ...
614 views

### Percentages from non binomial data: is ANOVA / Kruskal-Wallis appropriate?

I know ANOVA with percentages as already been discussed (Using ANOVA on percentages?) and (ANOVA-like test for bounded variables (percentages)), but the variables seemed different from my case. ...
487 views

### About Kruskal-Wallis, Mann-Whitney U and multiple comparisons correction

I have 5 independent samples which I want to compare, to define if there are significant differences in the distribution of values across samples. The samples' sizes are: 4562, 1116, 314, 151, 77 I ...
2k views

### Kruskal-Wallis Test and Mann-Whitney U Test

I have a three samples of data where each has a non-normal distribution: I want to determine whether the samples differ. Therefore I apply the KW test and it gives me a significant value, i.e. the ...
66 views

### Kruskal-Wallis and Negative binomial regression do not agree

I am comparing the number of broods made by dung beetles (Brood_Number) across three temperature treatments (Temp_Offset, a 3 ...
15 views

### Why several studies change logical paired/unpaired assumption from omnibus to post-hoc?

There are several studies of highly-referenced researchers where a paired post-hoc test (e.g. Wilcoxon signed-rank) follows the omnibus unpaired test (e.g. Kruskal-Wallis): From Huang et. al "THE ...
367 views

### Should there be agreement between NB GLM and Kruskal Wallis for categorical variable levels?

Briefly, my question is whether the results of a GLM (negative binomial) for a categorical variable should agree with the results of a non parametric test--in this case a kruskal-wallis test. This ...
348 views

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### Variance assumption and normal assumption not met, Kruskal or Welch-Anova?

I have 7 different groups of playing time data that is not normal. Lets say its really not normal..like a lot. The variance is also not equal and fails the bartlett test by a landslide. Sample ...