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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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Using Multiple Comparisons for Kruskal Wallis Follow up analysis

I am performing the Kruskal Wallis test on ~100 samples and wish to group statistically ‘similar’ samples together. The method I am using is described in Andy Field’s ...
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Pair-wise ANOVA or non-parametric comparison

I'm doing an experiment with 7 groups (batches) of 12 measurements of a certain chemical, where one group (b0) is considered the baseline case. The research question is to find out which groups have ...
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Why does the Dunn's pairwise post-hoc test identify significant variables that the Kruskal-Wallis H-test did not?

I have values for 9 landscape metrics that I am comparing across 5 disturbance intervals (20% increments). My data is not normally distributed. I have six subsets (based on natural regions). Two ...
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Meaning of chi-squared in R Kruskal-Wallis test

I have a simple question to ask, I think it was not covered in other questions. I am running a Kruskal-Wallis test in R, using the function kruskal.test. The output gives me the p-value and a chi-...
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Non-parametric test for interaction effect

I have a relatively small data set with quality ratings (dependent var), for different compression methods (independent var 1) applied to different types of video (independent var 2). My first ...
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23 views

ANOVA with post hoc for non-normal data with unequal variance

I have 200-some variables with 25,000 observations in each of 4 categories. For each variable individually, I need to identify where we have variability between categories. Therefore, I need an ...
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22 views

Is my analysis approach and decision valid?

I'm busy with a class assignment and I would appreciate a second pair of eyes on my analysis approach. A part of me feels that I'm overthinking this or have done an unnecessary test. Context: Use 4 ...
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Find joint distribution for two different cases Kruskal Wallis

I'm a bit stuck with my homework in a subject called "Non-parametric Statistics". The task is related to Kruskal-Wallis test. The task is as follows: Let's look at the comparison of 3 independent ...
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Can I use both parametric and non-parametric tests?

I have 3 variables, A1, A2 and A3 A1 is temperature A2 is month A3 is location A2 has 2 months - March and May. A3 has 2 cities - Chennai and Dubai. My data is ...
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Is it okay to use non-parametric tests on normalized data?

I'm doing experiments with 3 conditions: A, B, and C. I have done the experiment 3 times, so each condition gets 3 values for a total of 9 values. Each value is actually an average of 5 measurements. ...
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multiple comparison with controls - kruskall wallis or mann whitney + bonferroni

I have a test group and two control groups. I would like to compare: test vs control group 1 test vs control group 2 and I don't need the result from control group 1 vs group 2. Therefore, in this ...
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Is it possible to calculate a confidence interval related to a significant p value from the kruskal wallis test?

I have run the nonparametric Kruskal Wallis test with pairwise comparisons in SPSS to understand if my 3 groups of survey participants were different in their responses to a range of 5 point ordinal ...
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266 views

Wilcoxon Rank Sum test unequal sample sizes

I am comparing two sets of data using the Wilcoxon Rank Sum test. Although the distributions appear to be quite different, the p-value is quite high (0.344). This is the line of code being used for ...
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comparison of multiple groups when the dependent variable is a percentage

I am measuring the proportion of different types of bacteria killed by 4 different antibodies (simplified for illustration) ...
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29 views

Significance testing on two groups (distributions) of many binomial distributions

Basically I have two (or more) different success probability generating distributions. In other words, there are two (or more) different (non-normal) distributions, which realize success probabilities ...
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1answer
246 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. ...
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For my data, should I use a Kruskal Wallis or one-way ANOVA test?

I read through some literature online and did some investigating on my data and the type of scales my data represents. In my data set, I have my independent variable called ASA status (this is a ...
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69 views

Are the results of my paired tests false positive?

I am dealing with a strange situation which I hope you can come up with a solution. I have 3 pared group(n=7 for each) which I tried to see if they are significantly difference and if so, in which ...
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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 ...
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What is the appropiate Non-parametric test for study with 3 conditions?

The IV has 3 separate conditions & the DV measures Pre & post scores (ultimately to see what condition has the biggest effect on the scores - if there is any). The data is non-parametric- ...
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Kruskal Wallis H test

I am doing a Kruskal Wallis H test, it looks like I am getting a significant difference between the non-vegetarian group and the vegan group. But not with the semi-vegetarian group and vegan group. ...
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1answer
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Accounting for measurement Bias across manufacturers and multiple treatments

I've been trying to figure out the appropriate statistical approach for the following problem from work (simplified here): I've got 5 manufacturers of a drug and each manufacturer makes their own ...
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171 views

Dunn's test of multiple comparisons

From the documentation page for the R function dunnTest from the package FSA: Performs Dunn's (1964) test of multiple ...
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Testing 3 Kruskal Wallis on 3 datasets that each has 3 treatments

I am not that experienced, but, I read a lot and seems am stuck to know if what i am doing is right or not. I have 3 datasets that each were initiated based on session duration. The 1st dataset has ...
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1answer
307 views

Understanding hypothesis testing (Kruskal Wallis, Mann-Whitney) when there are tied values

tldr: In Python's Scipy stats modules, the kruskal and mannwhitneyu functions will both raise an error if called with only ...
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1answer
58 views

Two-Way Non-Parametric Test for Non-normal Data?

I have an unbalanced design with two factors, gender and site. I'm trying to test for differences in a size variable. Levene's test reveals that the data has equal variances. However, log transformed ...
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Non parametric tests for relation/association between variable

What could be an appropriate test for checking whether there exist any relationship between Net Promoter Score ( Categorical in nature with 0 meaning detractor, 1 meaning Neutral, 2 meaning Promter ) ...
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Is it ok to re categorize my variables this way?

I have a 2^3 factorial design, where the dependent variable is binary, and the three independents are binary and I care about interactions. I've seen that you can use logistic regression, but I feel ...
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How can I test the effect of a continuous IV (as well as other IVs) on an ordinal DV?

I have two instruments: a test, and a survey. Each participant has a test score, out of 240 (or a percentage out of 100%, it doesn't really matter.) The survey consists of 5-point Likert-scale ...
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1answer
240 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 ...
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1answer
80 views

Kruskal-Wallis and non significant post hoc test

I am running Kruskal-Wallis tests in SPSS to compare answers to Likert items among 3 (variable 1) and 4 (variable 2) groups. I am not running ANOVAs because assumptions of normality and ...
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44 views

Statistical tests, when data are not normally distributed & variance is not equal

I have a data with two variables - one variable is quantitative, and one is nominal (4 categories). I ran the normality tests and it turned out that this quantitative variable is not normally ...
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Comparing 4 groups of unequal sizes and non-normal distribution

I have 4 groups of students. Each student was asked to give us the number of reports they wrote through the semester.The 4 groups have n ranging from 5 to 250 ...
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Is it possible to use a Kruskal-Wallis test with multiple independent variables?

For my study, I'm investigating whether student's scores in a task (expressed as a percentage between 0-100%) influence their responses to a survey. The survey has 19 questions, and they're Likert ...
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Is Kruskal-Wallis the right test?

I'm writing a research protocol and trying to work out the right test. Is there a significant difference between the success rate (dependent variable, ratio data) for different repair materials (...
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Parametric vs non parametric tests for Likert items?

I have conducted a survey and am now trying to figure out how to analyse the results. I have a series of 6-point Likert items, which I have coded like this: -3 Strongly disagree -2 Disagree -1 ...
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Kruskal-Wallis test for showing features can discriminate the classes

I'm working on a problem for classifying 3 gestures using the EMG signals obtained from muscles. Each of the gestures has 6 trials of around 6-7s duration. Each trial is divided into multiple ...
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Non-parametric, 2-way ANOVA with different group sizes? [duplicate]

I have five cohorts I want to compare, initially with one factor as measured by a test. I was going to use a one way ANOVA, however discovered that the distribution was not normal, so was directed ...
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1answer
291 views

Kruskal-Wallis vs Jonckheere-Terpstra Test

If we're doing a Jonckheere-Terpstra Test and a Kruskal-Wallis test at the same significance level, which one is more likely to reject the null hypothesis when it is actually true? From my ...
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Why is the Kruskal Wallis test statistic approximately chi-square distributed?

According to Wikipedia, the Kruskal-Wallis test statistic H is approximately Chi Square distributed under the null hypothesis. However I can’t find any resources explaining why that’s the case. I’m ...
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Collaborator pushing for robust sandwich estimator - is it appropriate?

I have a dataset that is survival data for 3 different treatments, single time point data (ie: % survived at end of treatment), with an n=10*3 for each treatment. This data is non-parametric, which I ...
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1answer
21 views

Which has more power Kruskal Wallis or Cox regression?

I am analysing behavioural data that is the latency for predators to consume prey within a ten minute trial. The data are not normally distributed, and I originally analysed them using Kruskal Wallis. ...
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2answers
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Friedman's test or Kruskal-Wallis?

I am investigating the effect of an intervention treatment on a group of samples over 5 time points (a period of 2 months in total) For example: Subject 1 - Timepoint 1 (Dose 1), 2 (Dose 1), 3 (Dose ...
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45 views

Statistical advice needed: How to assess relationship between the concentration of acid vs current detected by an electrical sensor?

I would really value advice on the best way to statistically analyze the following data from a study I have undertaken. The study is looking at whether an electrochemical sensor we have built can ...
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1answer
65 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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0answers
22 views

How to compare two ANOVAs with different deppendent variables

I have 3 groups of mice and we measured 2 biomarkers. I want to know if the groups differ more in biomarker 1 or biomarker 2. First, I run ANOVA separately for each biomarker, to see if the groups ...
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1answer
36 views

Can I run one way ANOVA at each of my time points?

Suppose that I have two or more groups of data (e.g. two or more cities with 10 sampled population each) and I want to test if they behave differently for a variable (e.g. specific crime) through the ...
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66 views

Breaking Ties before non-parametric tests

I have a bunch of data and when running Kruskal Wallis post-hoc nemenyi pairwise tests on them I get a ties. I'm by no means very fluent on stats so I've tried a couple of things to deal with this ...
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98 views

How to report statistically non-significant post hoc test after a statistically significant K-W test?

I conducted a Kruskal-Wallis test and the results were statistically significant. However, after conducting posthoc tests and calculating adjusted p-values for the test of mean difference between ...
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Is it appropriate to use Kruskal-Wallis test for one comparison and Wilcoxon Signed Rank Test for another?

I have a data set that I would like to perform several tests on to see if there are significant changes over time. I have replicated measures of 3 experimental ponds and 1 control pond that I have ...