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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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22 views

### Kruskal-Wallis test for Length vs Year test

I have a dataset of the lengths of a species which has a 1-year lifespan, going back 20 years. I would like to test if the lengths recorded each year are significantly different from one another (for ...
7 views

### 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: ...
13 views

### What test is the most appropriate in this design with multiple variables?

I have a test design in which I have 1 base condition and around 14 test conditions. Each of those 15 conditions has a total of 15 observation points (so equal sample size). The base condition ...
26 views

### Advise for two non gaussian distribution group

I have a dataset which test the introduction of a new measure of a luggage checking a local small airport, the aim is to conclude whether the new measure reduce the luggage checking time. My dataset ...
2k views

### Wilcoxon Rank Sum test unequal sample sizes [duplicate]

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 ...
14 views

### How to interpret the kruskal wallis test in r

I am trying to understand the results on the kruskal wallis test that are produced in R. The data that I am testing: ...
9 views

### In scipy why stats.kruskal can work with two populations?

Krustall-wallis testing should be working only at least with 3 populations.But here, it seems to accept 2. Krustall-wallis extends the Mann–Whitney U test, which is used for comparing only two groups....
11k views

### Are pairwise Wilcoxon tests a valid non-parametric alternative to Tukey's HSD test?

I am trying to identify significant differences between groups from normal and non-normal distributions. When the distribution is normal the workflow is pretty straightforward: ANOVA and after that a ...
12 views

### Is Serial Independence, an assumption in Friedman and Kruskal Wallis Tests

I understand that Friedman and Kruskal Wallis are non-parametric tests to see if different groups come from same population. I also gather from here that these tests are used to test for seasonality....
506 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 ...
78 views

### Effect size calculation for Kruskal-Wallis mean rank test

I have a published paper in which I'm attempting to calculate the effect sizes for various outcomes. For a pre-post scale, the authors report the sample size, mean rank, and p-value for an outcome (...
6k views

### How many « degrees of freedom » should a Wilcoxon rank-sum test have?

I would like to perform a Mann-Whitney U Test (also called Wilcoxon rank-sum test) on a weighted sample in R. Such a non-parametric test is required, as neither of the two variables used follow normal ...
542 views

### a not significant result from Mann Whitney U and Kruskal-Wallis test despite large difference in sample median values

I was really hoping someone could assist me with this as I can't find anything in my books/papers/online. I know from descriptive statistics that there is a large median difference in earnings between ...
235 views

### Kendall's tau or Kruskal Wallis Test?

I have data which is not normally distributed. Each participant ranked six actions in order of preference (so this is ordinal data right?) I want to see whether there is a significant difference in ...
41 views

### Can Kruskal-Wallis test be used in groups of different size?

I am trying to compare Likert-scale answers to a survey applied in 3 different cities: A, B and C. I arbitrarily chose twice as many respondents from A, for a total of 500 answered questionnaires in ...
621 views

### Kruskal Wallis or Manova

I have to analyse 8 independent variables (IV) toward 8 dependent variables (DV) in my research. The IV is nominal while DV are ordinal (likert-scale). I run the normality test and the result is zero (...
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 ...
47 views

### What to do when assumptions of both ANOVA and Kruskal-Wallis are violated?

I am trying to analyse whether three groups (samples sizes 27, 26 and 23) differ in their responses to 20 questionnaire items, each measured using a 5-point likert scale. The items are all ...
36 views

### What is exactly the non-normality requisite for nonparametric tests? [duplicate]

As the title says, what is exactly what is being tested before deciding to use a non-parametric alternative test (as Kruskal-Wallis for ANOVA, or Mann-Whitney's U for student's t)? Most sources are ...
40 views

### Statistical Analysis of 3 groups(parameterisation of same algorithm) under the same dataset: non-repeated measures or repeated-measures?

I'm analyzing the performance of 3 parameterizations of the same algorithm under the same dataset. This performance is user-evaluated under a single Likert-type item (5-values). Given the ordinal ...
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 ...
207 views

### ANOVA (assuming different distributions) vs Kruskall-Wallis and post-hoc tests

During stats courses on Uni I learnt (if I remember correctly and hopefully don't put my teachers to shame) that if you want to compare multiple groups with eachother you look at the residuals of an ...
30 views

### is Kruskal- Wallis test appropriate in this case?

Does this make sense, is this test appropriate in order to see how responses differ among more then 2 different groups? I have no experience working with SPSS. Is there any chance someone can help me ...
13 views

### Can I use UNPAIRED post-hoc analysis for PAIRED omnibus testing?

If I have a omnibus statistical test with unpaired assumption (e.g.Kruskall-Wallis), could I ever use the opposite (paired) post-hoc analysis? (e.g. Wilcoxon signed-rank for post-hoc analysis of ...
225 views

### Name of multiple comparison post hoc of Kruskal-Wallis test in R agricolae package

Sorry if it is a stupid question, but can anyone tell me if the the multiple comparison of Kruskal Wallis test in R Agricolae package is a specific post hoc test? How does it work? If it is a ...
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 ...
43 views

### Multivariate test for likert scale data in r programming

I have a data of likert scale type, collected to know the 'level of awareness of individuals' about various investment options. I want to check if there is significant difference in level of ...
446 views

### Slight inconsistency between the Kruskal-Wallis built-in R function and manual calculation

I'm confused by the following, and I haven't been able to dig up the answer elsewhere. I'm trying to learn R while doing some statistics, and, as an exercise, I try to double-check the results of ...
182 views

### Kruskal-Wallis: how to handle ties that might not be really ties?

I have data from a mass spectrometer that are precise to 6 decimal places and range from 0.1 to 10. However, some items cannot be measured by the mass spectrometer because they are "below the limit of ...
2k views

I would like to compare the means of three groups using the Kruskal Wallis test in R. My data looks like this: ...
50 views

### Comparing heteroscedastic groups with sample sizes from 1 to 24… No valid tests?

I'm comparing 1 continuous variable across 36 groups (nurses grouped into 36 hospital units). Several groups have only 1 observation, but most have more, ranging from 1-24 observations per group. ...
25 views

### Small sample size ANOVA

I am working with monthly results of some variables, and I would linke to compare weather 6 years are statistically different or not, so my saple size per group (year) is bounded by 12. I ran Shapiro ...
195 views

### Should I use one Friedman test or two Kruskal-Wallis tests on small sample?

I am looking at concentrations at 3 sites over 4 years, with 4 samples at each site. Because of the small number of samples, I believe I should use non-parametric statistical tests. My question is: ...
24 views

### Independent or matched groups?

A very beginner level question here: I'm trying to see whether there is a difference in how students assess the usefulness of 5 possible courses to be added to their curriculum. Each student was asked ...
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, ...
30 views

### 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 ...
31 views

### Is the ICC appropriate here?

I have N tissue samples, labelled as either A or B. 2 measurements are taken from each sample. The data is not normally distributed. I'm interested in 2 things: firstly, whether there is ...
39 views

### Post hoc for Levene test

I have a problem regarding my data analysis. One of my hypothesis is basically that my groups will differ in terms of spread of the scores, indicating that there would be a difference in extremity ...
37 views

### What is the appropriate test when dependent variable is ordinal binary and independent variable is continuous?

I am curious what is the most appropriate test to use when the outcome variable is an ordinal binary (test score of pass or fail) with a set of four unordered treatment conditions (A,B,C,D) as the ...
30 views

### Weighted Kruskal-Wallis Test and Questions

I am currently studying the prevalence of a particular disease among eight different subgroups (for example, the prevalence of hepatitis B among HIV+ patients, HIV- patients, etc.). Each subgroup ...
140 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 ...
674 views

### Comparing the means of 6 groups, binary dependent variable

I accomplished a field experiment which results in six differently treated groups (including one control group, each n = 300). Due to randomization all groups are expected to be equal in terms of ...
9 views

### Appropriate analysis for univariate proportion data and environmental variables

I'm new to statistics so am trying to choose the best analysis to find if; There is a difference between canopy cover (0-100%) at different sites There is a relationship between canopy cover and ...
18 views

### Friedman and Kruskal

I have a data with 4 groups and multiple variables with measured values. my groups are ES, EP, PP and PS. ES and EP are associated and PP and PS are too. So i would like to compare my groups in non ...
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 ...
57 views

### What test do I use for this? (NOOB biostatistics question)

Suppose I have some subjects and I give each of them a test. I would end up with a dataset like: ...
42 views

### Mann-Whitney (2 groups) contradicted by Kruskal-Wallis (3 groups)

We have two groups that are significantly different (tested with Mann-Whitney). When a third group is added, the Kruskal-Wallis tests provides a non-significant result. This implies that two or more ...
54 views

### Is this a valid approach to hypothesis testing

I have been a machine learning hobbyist for a while now and am attempting to formalise my understanding of the statistical foundations to data analysis and machine learning. My reading so far has ...