All Questions
Tagged with nonparametric multiple-comparisons
54
questions
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14
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When is Tukey post hoc test result identical to Games Howell post hoc test for Welch ANOVA?
In what situations is the Tukey post hoc test identical to the Games Howell post hoc test? I have an ANOVA analysis where HOV is violated and I have a statistically significant Welch ANOVA result. I ...
- 341
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0
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29
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Why does the Dunn's test in online calculator rejects the null hypothesis while my manual computations cannot reject it?
In my own manual calculations of the Dunn's Test in google sheet, using the formula from a YouTube video, I managed to calculate the same Test Statistic as the online calculator.
However, using the ...
1
vote
2
answers
356
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SIgnificant ANOVA but not significant post hoc ... what can I do?
I am analyzing some IHC data on the density of cells in two brain regions(factor 1) in two closely related species(factor 2). My data is composed of an n of 6 for each species and is not normally ...
3
votes
1
answer
57
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Bonferroni correction gives weird results in R
I have this dataset:
Treatment
data
T1
0
T1
0
T1
0
T10
0
T10
0
T10
0
T11
0.2
T11
0.2
T11
0.2
T12
0
T12
0
T12
0
T2
0.7
T2
0.6
T2
0.6
T3
0.8
T3
0.7
T3
0.8
T4
0.3
T4
0.3
T4
0.4
T5
...
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3
votes
1
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211
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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 ...
- 31
2
votes
2
answers
266
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Need for bonferroni correction
I need help understanding if I need to / how to apply a bonferroni correction!
I have one continuous variable and three unrelated groups that have completed scores on this variable (Groups: A,B,C). I ...
- 31
1
vote
1
answer
1k
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How to do pairwise comparisons for Kruskal Wallis test?
If the null hypothesis in the Kruskal Wallis test is rejected, How can we perform pairwise comparisons? Can we apply Dunnett's Test for that?
- 11
1
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2
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82
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Are t-tests good choices here?
I would like to test if two groups of participants (dark-eyed and light-eyed individuals) respond to a drug differently over time. The hypothesis is that the drug reaches its peak effects sooner but ...
- 13
1
vote
1
answer
43
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Which pair of two distributions are more similar?
Suppose I have two pairs of distributions: distributions A and B in Pair 1, distribution C and D in Pair 2. There are non-parametric tests to determine if there is evidence to say that the ...
- 125
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230
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On assumptions and calculation of O'Brien's "Global Statistical Test" for Multiple Endpoints Analysis
As I understand, O'Brien's Global Statistical Test (GST) (https://pubmed.ncbi.nlm.nih.gov/6534410/) for Multiple Endpoints Analysis is a method for mapping a multivariate problem on a univariate scale....
- 127
3
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1
answer
198
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Multiplicity correction after performing non-parametric tests
This is a theoretical question.
I am wondering if multiplicity correction is applicable in the case of non-parametric tests.
I have performed some Mann-Whitney U rank test on two independent samples ...
- 120
1
vote
1
answer
2k
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How do I interpret the p-value in a Dunn-test?
I conducted a Kruskal Wallis test for my sample sizes, and this is what I got:
Kruskal-Wallis chi-squared = 12.138, df = 4, p-value = 0.01635
The p-value is below 0.05, so I know there is a ...
- 15
4
votes
2
answers
2k
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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 ...
2
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0
answers
465
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Multiple comparisons version of Kolmogorov-Smirnov test
Suppose $\mathbf{y}_{i} $ and $ \mathbf{x}_{i}\,$ are length-$m$ vectors and $D_{i}$ is some arbitrary distribution $(i=1,...,N)$. I would like to conduct the following hypothesis test:
$ H_{0}: \...
- 388
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1
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107
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Calculate fraction of multiple tests for which the null hypothesis was rejected
Consider a test (e.g., a permutation test) that tests, at the individual level, if a binary event occured or not.
A paper that I was recently reading, for example, tested whether or not a pair of two ...
- 3
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2
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60
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Question on non-parametric tests and comparing two groups across countries
I have a dataset with every election in various countries between 1900 and 2010. There are about 300 elections but only between 20-40 elections in most countries. I am trying to test whether ...
- 39
2
votes
1
answer
3k
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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 ...
- 23
1
vote
2
answers
3k
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Multiple comparisons for not normal and heterogeneous data
I have a data set that has 3 groups and a single variable. Under normal circumstances, a one-way ANOVA would be used for comparisons between my three groups. HOWEVER I ran a Shapiro-Wilk test for ...
2
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1
answer
2k
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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 ...
0
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0
answers
147
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Kruskal Wallis test gives significance, multiple comparision table doesn't
I'm comparing physico-chemical properties of 8 different kefir samples like viscosity at different storage times. I have 4 viscosity measurements for each group. When I conduct Kruskal Wallis test; ...
- 1
0
votes
1
answer
62
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Nonparametric multiplecomparison tests for discrete data
Suppose I have $K$ populations each consisting of $n_i$ ($i=1\dots K$) observations $x_{j,i}$ ($j=1 \dots n_i$). Each observation is comming from a Bernoulli distributed random variable $X_{j,i} \sim ...
- 129
3
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0
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446
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Multiple comparisons between two groups (non-parametric)
Update Added more details about the Experimental setup.
My experiment comprised two groups, control (N=25) and experimental (N=26). Each participant belonged to one group. Their performance has been ...
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1
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0
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30
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What test should one use when dealing with different treatments in plant clones?
In an experiment involving plant clones there are: 20+ treatments, 5 technical replicates for each treatment (plant clones in which the treatments were tested).
Variable of interest is Biomass.
Due ...
- 133
1
vote
0
answers
149
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Pairwise non-parametric test?
I have 5 groups of patients (different sizes), for which I measured some property that is continuous but not normally distributed. I would like to compare every pair of groups in respect to this ...
- 11
2
votes
0
answers
43
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Which test to use to detect if a process has significantly more errors than another?
A have a set of machines running a particular software. I want to do something that's called "canary deployment".
This consists of deploying the new version of the software to a subset of machines ...
- 121
1
vote
1
answer
45
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How can I run multiple tests in a valid and random fashion?
I hope this is the correct place to ask this question. I'm currently doing research where I'm comparing two groups on their EEG frequency spectra. I wasn't too sure how to approach this.
Data:
I ...
- 299
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votes
1
answer
347
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How to compare several means to control when the distribution is not normal and sample sizes are unequal?
I have a large dataset (n = 170,000), distributed roughly equally among 5 groups (each is 34,000 ± ~1,000). I want to compare whether the means in any of the first 4 groups are different from the ...
- 133
1
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0
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31
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Nonparametric test for 1 categorical IV and multiple binary DV:s?
I have a dataset where test subjects have answered three different questions (my IV). The answers to each question are scored on 10 different variables (presence or absence of 10 concepts in the ...
- 111
1
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0
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1k
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Pair-wise comparisons in non-parametric ANCOVA in R/SPSS
I'm running a non-parametric ANCOVA in R. I'm using the non-parametric ANCOVA from the fANCOVA package. https://cran.r-project.org/web/packages/fANCOVA/fANCOVA.pdf
I'm getting the results below. Now I ...
- 21
2
votes
2
answers
572
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Can I use a permutation test to determine whether overlap of 2 distributions is significant?
I am evaluating whether two distributions are different from each other. For example, histogram A (B) has most of its binned values between 10-15 (15-20). So, histogram B has a right-ward shift in ...
- 21
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1
answer
90
views
How to interpret results of differences of differences in interactions?
I have a dataset composed of 2 factors of several levels each (i.e. exercise[A-B-C] x muscle [1-2-3-4-5-6]. I'm interested on the effect of the different exercises (A,B,C) on the muscle activation ...
- 11
2
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0
answers
116
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How to adjust ratings of N items by pairwise comparisons
I have been keeping a list of movies I've seen in a spreadsheet and assigning them numerical rankings that approximate how I feel about them. A few years ago I implemented a program to read in the ...
- 1,347
4
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0
answers
238
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multiple Kruskal-Wallis instead of ANOVA for non-normally distributed data
Apologies in advanced if I supply too little or vague information, since I am a complete newbie in stats and using this forum.
So I did a study which evaluated psychopathic personality traits, ...
- 41
2
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0
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57
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group comparisons - normality of the distribution
When comparing 3 different groups on a certain variable and one of the groups does not have a normal distribution (as verified by the Shapiro test) whilst the other to do, would you think it is best ...
- 305
2
votes
1
answer
3k
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what test to use for comparing count data across multiple groups
I have five groups of students and 40 in each. And we counted the number of references spelling mistakes in their homework. We would like to compare to see if there exists any groups differences in ...
- 229
4
votes
1
answer
10k
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Why run a post hoc wilcoxon signed rank test after Friedman test, why not just skip to Wilcoxon sign test instead?
I understand that one is required to run post hoc tests after the Friedman test. For example, while the Friedman test may find a statistically significant change amongst 3 treatments, one may follow ...
- 41
0
votes
1
answer
22
views
Multiple Comparisons test strategy
I have a test data with 3452 subjects , I have 5 different algorithms that detect the presence or absence of a disease.
...
- 25
1
vote
1
answer
164
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multiple comparison for discrete nonparametric distributions
I have $N=24$ controls and $M=10$ patients. ($M$ can be $20$ later.)
Each subject has one $3D$ image, each element of the image is a discrete value (integer) ranging from $0$ to $4$ $[0,1,2,3,4]$. It'...
0
votes
2
answers
2k
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Pairwise non-parametric test for small sample sizes
I was asked to check a small dataset (3 replicates for 5 treatments, each) for significant outcome differences.
I give an example:
The variance within replicates in the data cannot be assumed equal, ...
- 258
4
votes
0
answers
543
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Multiple comparison of non-normal, heteroscedastic data. What test should I use?
I have a set of brain pathology data. These were obtained by counting certain parameters in the brain. Due to availability of human brains, the amount of cases vary a lot across the different groups ...
- 51
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0
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398
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Kruskal-Wallis post hoc comparisons different results in different software used
I'm having some trouble analyzing my data because when I use StatSoft Statistica and run a Kruskal-Wallis, I get one set of values for multiple comparisons, but when the same analysis is run in XLSTAT ...
- 81
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2
answers
5k
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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 ...
- 185
2
votes
2
answers
98
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Multiple models compared over same data
My question boils down to if I really have to use a multiple comparison adjustment or not, and if so, how I can do this to retain as much power as possible.
I have multiple models (say 5) that are ...
- 23
2
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0
answers
339
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Multiple comparisons on nested subsets of data for a non-parametric test
My problem: I'm using data sets where some are nested in a non-parametric test that expects independent data sets. How can I correct for that in a way that is reasonable? Or even better: What would ...
- 602
12
votes
1
answer
10k
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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 ...
- 121
1
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2
answers
3k
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How to compare multiple proportions between multiple groups
I measured prey capturing success (=proportion of successful captures divided by the total number of prey captured) in four fish species (species 1: n=19, species 2: n=18, species 3: n=4, species 4: n=...
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4
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16k
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How to correctly apply the Nemenyi post-hoc test after the Friedman test
I'm comparing the performance of multiple algorithms on multiple data sets. Since those performance measurements are not guaranteed to be normally distributed, I chose the Friedman Test with the ...
- 602
8
votes
1
answer
13k
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Differences between Dwass-Steel-Critchlow-Fligner and Mann-Whitney U-test for a post-hoc pairwise analysis
If you have one control and four groups of patients with a non-normal small sample size, there are differences in these tests for a post-hoc analysis after Kruskal-Wallis?
- 81
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votes
1
answer
913
views
Non-parametric paired analysis of variance with unequal data
I have tried to search, but couldn't find an answer for my problem.
I have data from different subjects that are exposed to different conditions. But they are exposed to the different conditions ...
- 71
1
vote
1
answer
240
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Comparing prices between different stores (non-parametric models?)
I have thousands of product info in a database with category, title, description, make, model, price and store name. I have grouped those products by store names and it seem to span to 4 stores. So ...
- 111