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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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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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Dunn's post hoc test sig difference - what next?

I have 3 unbalanced groups and I want to check for differences between these across test conditions. If I don't see any significant differences, I will include all my subjects in one same group and ...
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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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Kruskal–Wallis vs Mann–Whitney when comparing pairs

I am wondering the following. Given a dataset of measurements of one sample under 7 different conditions, which test is the most accurate and appropriate to use when comparing each two of the ...
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3answers
136 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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59 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
120 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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1answer
2k 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
86 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 ...
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1answer
346 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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510 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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430 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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534 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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598 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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497 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 ...
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2answers
806 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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435 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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118 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
2k 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
2k 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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216 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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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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156 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. ...
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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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172 views

Why does power reduce when increasing the number of post-hoc comparisons?

I'm performing a Dunn's post test comparison of my data after a Kruskal-Wallis test (4 groups, treated and control each one has drug and vehicle injection). The comparisons I've been doing are <...
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1answer
3k views

Dunn.test in R: are adjusted p-values corrected for number of comparisons?

I've performed a post-hoc Dunn's test with Sidak adjustment using the dunn.test code for R. There are three groups in my comparison and I understand from the R help files that the lower number in the ...
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2answers
2k 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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3k 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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2answers
449 views

What means “CDF of one group does not cross the CDF of the other” from the dunn.test description? [duplicate]

From the dunn.test manual: "CDF of one group does not cross the CDF of the other". What this means? I am not a statistician, but I want to understand. What I found ...
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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 ...
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790 views

Multiple Comparisons testing and Dunn's Test

I have 8 different groups of individuals, each with a pre- and post-treatment measurement. The data are non-normal, so I used a Jonckheere-Terpstra test to test for an ordered alternative and ...
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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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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
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 ...
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1answer
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 ...
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1answer
81 views

Five different groups

We are running a study which investigates platelet aggregation changes during three trimesters of pregnancy and postnatal period. Then we compare each of these phases to control non-pregnant women. ...
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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-...