Questions tagged [dunn-test]

Dunn's test is a non-parametric pairwise multiple comparisons procedure based on rank sums, often used as a *post hoc* procedure following rejection of a Kruskal–Wallis test. As such, it is a non-parametric analog to multiple pairwise *t* tests following rejection of an ANOVA null hypothesis.

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1answer
66k 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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18 views

Is the Conover-Iman post-hoc test is better to use than Dunn's with small samples size after the KW test since it use the t-test on the ranks?

I know that we use the t-distribution to be able to know if two small-size samples with a normal distribution (n < 30) are different or not (Student's t-test). If we have a bigger sample with a ...
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230 views

Which pairwise comparison tests are best to use after the Kruskal-Wallis test (Dunn, Conover-Iman or Steel-Dwass-Critchlow-Fligner test)?

I have 3 sampling sites where I took 3 water samples in each site. I chose to do the Kruskal-Wallis test to find out if there is a significant difference in total nitrogen between the sites. I did not ...
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112 views

Why are the adjusted P values using the Benjamini-Hochberg procedure in dunn.test and p.adjust different?

After a Kruskal-Wallis test, I wanted to do a posthoc Dunn's test with the Benjamini-Hochberg correction, which I did with the R package dunn.test. I noticed an adjusted P-value being higher than 0.05 ...
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1answer
28 views

Adjusted significance level in SPSS for Kruskal Wallis Post Hoc Test - Bonferroni adjustment

I am making a pairwise comparison using Dunn's post hoc test with Bonferroni correction. However, I am a bit confused on the interpretation of the adjusted significance on SPSS. I am making 10 ...
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1answer
46 views

How to report? Significant difference for Kruskal-Wallis test, but not for ad hoc pairwise comparison with Bonferroni

I performed Krusal-Wallis test in SPSS and got a borderline significant P (0.042). then, the post hoc pairwise comparison with Bonferroni-Dunn correction showed no pairwise significant difference. I ...
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31 views

Should I rank my data before doing post hoc Dunn test?

I am trying to compare multiple algorithms using the Friedman test and post hoc Dunn test. I know that we should use the rank of our data before performing the Friedman test, but should we rank the ...
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1answer
46 views

Why does my omnibus test do not agree with post hoc test?

So I am running a simple Dunn's Test on my data. After running the Kruskal-Wallis H Test, it returned a result ...
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73 views

Analysis of variance with unbalanced design and heteroskedastic data

I am looking for a way to analyse the differences in vegetation carbon stocks (named after 'OC_TOT') among different vegetation types (named after 'Facies') and islands (Guadeloupe and Martinique). ...
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15 views

Bonferroni adjusted p values (from a dunns test)

Are these P values to the same alpha value; ie, if adj p > 0.05 then there is no significant difference? also what does it mean when p = 1 (because this has happened for some of mine yet none of ...
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1answer
79 views

How to get the standardized z-statistic from dunn.test-package in R?

Sorry if this is a trivial question, but I couldn't find anything on it. I am running a Dunn-test with the dunn.test-package: ...
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Can I use Dunn's Test to compare weighted means?

I am interested in comparing the weighted means of multiple groups. The underlying data are not normally distributed, so I'm opting for a non-parametric test similar to the Kruskal-Wallis test. ...
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46 views

Report significant Friedman test or non significant post-hoc tests? Report both in the manuscript? What are your experiences?

I am using SPSS. On my dataset I get a highly significant Friedman test(p<0.001) but post hoc pairwise tests with Dunn-Bonferroni (in SPSS this test is set as the default test after a significant ...
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1answer
700 views

Is Dunn-Sidak approach in MATLAB multcompare identical to so-called Dunn's test?

I've asked the same question elsewhere. These two articles recommend Dunn's test as non-parametric post hoc multiple comparison test following Kruskal-Wallis test. How the Dunn method for ...
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1answer
274 views

Dunn test and specific comparisons

What I need is a non-parametric alternative for Dunnett test to compare several groups with a control group (not all pairwise comparisons). And I realise that a specialised test is more appropriate ...
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22 views

Limiting comparisons for post-hoc Dunn's Test

I used the dunn.test() function to run post-hoc comparisons after significant outcomes in an ANCOVA with ...
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1answer
35k 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 ...
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1answer
94 views

Choosing the right test to compare the difference in mean between 3+groups according to the data we have (param vs non-param, sample size..) [closed]

I hope everyone who reads this is fine. I come to you for help, I am a student in data analysis, but I am not yet familiar with everything, especially regarding tests. I have 3 groups of independent ...
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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 ...
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1answer
241 views

When doing FDR correction in graphpad prism after Kruskal-Wallis does the programme automatically perform a Dunn test?

I used the Benjamini-Hochberg FDR correction in graphad after performing a Kruskal-Wallis test. This gives me a list of individual P-values. The graphad website says that if you select the FDR ...
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1answer
159 views

Likert Analysis - Dunn's Test (Stata)

Similar to previous questions but I'm still a little confused as to whether I've followed the right process/understood the results correctly. For a research project I'm conducting I used Likert ...
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1answer
492 views

Is dunn.test for two samples equivalent to wilcox.test?

I know that dunn.test is generally used as a post hoc after Kruskall Wallis to see which groups are different, but to generalize the function I am writing, I was wondering if when only using two ...
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Is Kruskall-Wallis H test suitable to influence marketing plan after survey?

I've run a survey which received around 270 responses from a population of around 5,500. The survey asks brief demographic questions followed by opinion questions, akin to the following: Demog Q 1: ...
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Difference in adjusted pvalues for comparisons between classes when using complete data and only two classes using dunn.test::dunn.test() in R

I am studying carbon content between land cover classes in patagonia and I want to test for statistically significant differences in my data. Since my data doesn't follow a normal distribution, I ...
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Statistical Comparison of Algorithms by User Ratings

I have an experimental setting where I compare 3 algorithms on the same dataset(n_sources), through user subjective evaluation of the produced outcomes(each algorithm does a different kind of sound ...
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3answers
2k views

Dunn's test: is it appropriate to use p-values to interpret relative between group similarity

For a set of data that I collected, I used the Kruskal-Wallace test to determine whether there were between-group differences in the parameter I measured. It returned a significant result, so in order ...
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1answer
6k views

What are the (practical) differences between Tukey's HSD and the Dunn-Sidak correction procedures?

I have a data set with three groups, one of which is a control and the other two groups have been administered either a moderate or a high dose of a drug. The data are not normally or log-normally ...
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1answer
3k views

Dunn's test p-values in R are exactly half those in SPSS and GraphPad for the same data

Firstly, this is my first post to Cross Validated, so apologies in advance if I have infringed any conventions. I am writing up a PhD thesis on aspects of biomedical research, and use R for my ...
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1answer
4k views

Multiple comparisons with many groups

I would like to determine if using multiple comparisons test would be appropriate for my data. I used the Kruskal-Wallis test to determine if there were differences in mean inhibition among $17$ ...
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0answers
94 views

Kruskal Wallis test or Friedman for multiple preselected unmatched pairs

I am unsure whether I should use Kruskal Wallis test or Friedman's test in the following case, where I am required to use a non-parametric test while compensating for multiple comparison with a post ...
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1answer
3k views

Interpreting the results of the Dunn test

I've seen some answers that come close to what I'm asking but not quite. I've run a Kruskall-Wallis test that rejected the null hypothesis. Now, I've run the Dunn test, but I'm wondering if I am ...
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1answer
728 views

Problem with Dunn's post hoc test to compare a lot of groups?

I have a dataset were people sampled litter at 12 different locations. As the data does not have homogeneous variances I performed a Kruskal Wallis rank sum test (which came up significant) and ...
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4answers
16k views

Friedman's test is very significant, but its post hoc comparisons (SPSS) are not significant

I ran a non-parametric Friedman's test for my data in SPSS 22 and significantly rejected the null. That would mean that among the $k$ paired samples (3 in my case), there should be detected at least ...
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1answer
129 views

Is it appropriate to remove meaningless pairwise comparisons from a post-hoc analysis before correcting for multiple comparisons?

I have four individual groups with two controls and two interventions. The second control group is specifically related to the first the intervention group, making the comparison to the second ...
12
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1answer
10k 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 ...
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4answers
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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 ...
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0answers
682 views

Does Dunn Test require multiple comparisons correction?

If I compared 8 groups with a single Kruskal-Wallis test and it came back positive (<0.05), and then was interested in conducting a Dunn Test to determine which pairs differed between each other, ...
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0answers
585 views

Dunn-Bonferroni: All three differ significantly?

I have this huge knot in my head while writing my thesis atm. I am totally untalented when it comes to statistics, so it could be that my question is easy to answer for some of you. I did a Kruskal-...
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595 views

How do I know which of my groups are significantly different? Kruskal-Wallis, Dunn's test

Answers to other posts that are almost identical to my question are still confusing to me... my data is nonparametric, unequal sample size, unequal variance, so I've decided that kruskal-wallis is ...
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0answers
1k views

Comparing count data from multiple groups, Kruskal-Wallis with Dunn post-hoc or GLM with Poisson distribution?

Stats novice. I am comparing counts of microplastic artefacts from multiple independent sites, my null hypothesis is that there is no difference in counts between the sites. So far I have tried ...
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0answers
802 views

Mann Whitney U test or Kruskall-Wallis + Dunn test as a post hoc?

I performed a set of inhibition experiments where Lactobacilli supernatants where tested against a pathogen cell culture. These experiments were carried out in a 96-well plate where pathogen was ...
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0answers
651 views

How to read the result of of posthoc kruskal dunn test?

How to read the result of of posthoc kruskal dunn test? Specifically, what do the values in the table below tell me? I have 6 treatments and I first did a Kruskal-Wallis test to confirm that the ...
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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2answers
1k views

Is it possible to get a CI for the difference in median response between two groups via Dunn test?

Dunn test for two groups is equivalent to Kruskal-Wallis. The null is the absence of stochastic dominance, but if we impose some more restrictions we can assume that the null is the equality of ...
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149 views

Multiple comparisons and power analysis

I would like to compare 4 different groups for 10 different variables (the biodistribution of a material in different organs). Someone suggested me to use a Kruskal-Wallis test with Dunn's post-hoc ...
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1answer
3k views

How to report the results of a Dunn's multiple comparisons test

I am a bit confused about Dunn's Multiple Comparisons test. My data are non-normal, and I'm comparing the sizes of fish in different years. Here's what I'm not sure about: 1) What is compared? Dunn (...
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If two groups are significant in a Mann-Whitney U test, should they also be significant in a Dunn's test?

I just ran across something that I thought was interesting but don't fully understand. I have some categorical data that I am comparing in R. I use a Mann-Whitney U test when there are just two groups ...
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0answers
242 views

Dunn's test null hypothesis

According to this link: https://stats.stackexchange.com/tags/dunn-test/info The null hypothesis for the two group Dunn's test is that one group does not stochastically dominate the other. Is this ...
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2answers
3k views

Is dunn.test a suitable alternative to kruskalmc in pgirmess package?

I'm trying to run the krushkalmc method after running kruskal.test as part of my analysis with the Kruskal-Wallis rank sum test. I have data with a small sample size that also does not have a normal ...
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0answers
172 views

Choosing to adjust or not after Kruskal-Wallis rejection

I have a series of data (4 numerical variables) and 4 categorical variables (with multiple factors each). I need to test for differences between various subsets based on the categorical variables. ...