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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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18
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1answer
49k views

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-...
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4answers
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 ...
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3answers
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?
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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 ...
9
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4answers
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 ...
6
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2answers
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 ...
6
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2answers
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?
6
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2answers
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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 ...
9
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1answer
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?
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2answers
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 ...
12
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1answer
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 ...
5
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2answers
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 ...
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2answers
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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 ...
3
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1answer
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 ...
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1answer
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, ...
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1answer
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. ...
13
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1answer
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?
11
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1answer
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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 ...
7
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1answer
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 ...
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4answers
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 ...
3
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2answers
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 ...
2
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1answer
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. ...
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4answers
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) ...
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4answers
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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 ...
4
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1answer
722 views

Kruskal Wallis test with high type 1 error

using this code ...
3
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1answer
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 ...
3
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1answer
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 ...
2
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1answer
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 ...
2
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2answers
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 ...
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1answer
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)...
0
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1answer
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 ...
0
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1answer
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 ...
5
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1answer
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 ...
5
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2answers
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 ...
5
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1answer
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:...
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3answers
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 ...
3
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1answer
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 ...
3
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2answers
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 ...
2
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0answers
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. ...
2
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1answer
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 ...
2
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1answer
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 ...
1
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1answer
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 ...
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0answers
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 ...
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1answer
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 ...
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1answer
348 views

What is a one-way ANOVA on the ranks of the observations

While reading this link: http://www.statsdirect.com/help/Default.htm#nonparametric_methods/kruskal_wallis.htm, I came across the following: ...
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0answers
1k views

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 ...
0
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0answers
1k views

Chi-Square value in Kruskal Wallis test very large

I am comparing measurements of 12 different groups to one another. My distributions are not normal and my Levene's test is significant - even after data transformation. I am therefore doing a Kruskal-...
0
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1answer
69 views

Non parametric analysis

The my dataset is not normal distributed. In order to apply a non parametric analysis, exist only the Kruskal Wallis test or others? I need to find a test similar to ANOVA to apply a dataset not ...