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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16 views

Proper name for the variant of Haldane estimator for handling empty cell in a 2xn contingency table

I am using R and survey package to analyse a survey that several 2xn contingency tables need to be analysed using Chi square ...
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383 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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Post hoc for Kruskal-Wallis Test

What post hoc test can I do after Kruskal-Wallis? Is there a post hoc test for non-parametric test? Some says there's none. I ran Kruskal-Wallis test and as a result the null hypothesis was ...
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Normality of distribution: Shapiro-Wilk and Levene tests

I have Likert-scale data from an experiment with 5 conditions, each of which has a different treatment and one is a control group. The goal is to compare the effect of the treatment between the ...
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141 views

Statistical test for data where groups have non-normal distributions with varying distribution shapes

I have between-subject design with 3 different groups where I capture interval data (on scale 1-4 where equal spacing amongst scores can be assumed). The data in groups is not normally distributed ...
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529 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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2k views

Wilcoxon-signed rank vs Kruskal-Wallis?

I am rather stressed out about my methodology. For my PhD I ran a year long literacy intervention (small scale longitudinal study) that was supposed to test the rate of change in individual students' ...
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Are different activities done by the same person independent or dependent variables?

I have 4-point ordinal data on users' opinions about various apps which they use, and I want to run significance tests on the ratings given to each app. None of the apps requires the others to be ...
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Test for Statistical Differences Among GLM Modeled Data

I have three independent data groups - the groups are comprised of census tracts. Each data point (tract) within each group has a modeled estimate of disease prevalence (% pop that is obese as an ...
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444 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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236 views

P-value correction/adjustment for multiple groups and high number of tests

My dataset is 5175 rows by 16 columns. Each row is a biological pathway, each column is a sample (n=4/group), and each observation is an enrichment score. Due to the small sample size and non-normal ...
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333 views

How to report results based on Likert item group differences?

I collected Likert Item responses to a series of questions. My goal is to demonstrate that some of the groups are different from the others. The dataset has the following format: ...
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822 views

How do I adjust for covariates using Kruskal Wallis in SPSS? [duplicate]

Do i need to do another test after KW to account for covariates or is there a way to account for covariates when doing the initial KW test in SPSS?
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How to determine if my data samples are independent and whether multiple kruskal-wallis tests will increase family wise error?

I ran multiple K-W tests on my data and realized that I didn't account for family-wise errors. However, everything I've looked at have said that I won't have an increase in error rate if my data ...
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238 views

Kruskal-Wallis Test for H0: ranks differ between groups and H1: ranks do not differ

The traditional Kruskal-Wallis Test tests null hypothesis $H_A$: ranks do not differ between groups against the alternative hypothesis $H_B$ in which the ranks differ between groups. However, what if ...
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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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Post Hoc Kruskal - Wallis test for compare mean ranks

Can I use multiple comparison (Post Hoc Test) if Kruskal - Wallis Test can only be used to compare mean ranks?
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603 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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What statistical test should I use for subgroup analysis/correlation?

I am a conducting a four group randomized survey-based study. In the first group, I explain a situation, and then ask respondents their willingness from 1-10 to take a medication. In the second group,...
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565 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 ...
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Why would the median be used to summarize ordinal data instead of the mode?

I am working with ordinal data (produced from Likert-types scales). I am of the understanding that results should be presented as a mode, which makes sense to me. However, when working in SPSS and ...
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67 views

Testing for difference between count data where there are missing values (i.e. 0 in some cells)

I have collected data on different bumblebee species visiting a particular species of flowers over the course of the day. Counts were made every 10 minutes for 6 hours. I have now put all of my data ...
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Kruskal-Wallis test: assumption testing and interpretation of the results

There is a chapter on the Kruskal-Wallis (KW) test on the website influentianl points, and there are some quotes I'm not sure I understand correctly: Quote 1: Some authors state unambiguously ...
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232 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 ...
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513 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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317 views

Interpreting whether distributions of scores are similar

As part of a survey I had to conduct Kruskal-Wallis H test. The aim of my study is to understand whether the current waste management practices in households have any effect on people's interests in ...
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Result of Kruskal-wallis test: No significant difference among groups

If I get no significant difference when using Kruskal- Wallis test, is any post hoc test mandatory?
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245 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 ...
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10k views

Should I report non-significant results?

I've run a Kruskal Wallis test, and for some of the questions the p value is not significant. Would I report this in the same way as if it was significant, stating the df, test statistic and p-value? ...
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5k views

Reporting Kruskal-Wallis Test Result with Pairwise Comparisons

I have run a Kruskal Wallis Test on my data and it is significant at p=0.00. I have currently reported the output as H (3) = 18.047, p<0.00. However, I now need to see where the difference between ...
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357 views

Why isn't it possible to use fractional weights for Kruskal-Wallis test?

When I try to run a Kruskal-Wallis test on a sample with fractional weights, SPSS throws the following warning: ...
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204 views

Kruskal Wallis test for repeated measures

How do you perform the Kruskal Wallis test with 2 repetitions for the same patients? I have applied it on the difference of scores but what happened if there are more than two repetitions?
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How to calculate the Sample Variance for the Kruskal Wallis Test (with Ties)

The ranks are: Rank Group 1: 13, 15.5, 18, 21.5, 9.5 Rank Group 2: 4.5, 11.5, 18, 20, 18, 6.5 Rank Group 3: 3, 21.5, 11.5, 9.5, 15.5, 14 Rank Group 4: 6.5, 8, 2, 4.5, 1 So the means of ranks are:...
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Low number of observation while comparing means

I would like to test the difference between the mean weights of 4 groups So, my dependent variable is continuos, but there are 3, 12, 26 and 56 observations in my groups. Should I use One-way ANOVA or ...
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387 views

Should there be agreement between NB GLM and Kruskal Wallis for categorical variable levels?

Briefly, my question is whether the results of a GLM (negative binomial) for a categorical variable should agree with the results of a non parametric test--in this case a kruskal-wallis test. This ...
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65 views

Comparison between groups

I have to compare three groups. Three measurements using 3 different methods on the same subjects. The variables are not normal, and the measures concern the same people, so dependent samples. I can ...
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821 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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448 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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119 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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Is it appropriate to apply ordinal regression to a continuous response “as is” (with no ties)?

The goal is to run non-parametric general linear model with no restrictions on the design (e.g. not limited to one-way ANOVA as in Kruskal-Wallis test; quantitative factors should be admissible, etc) ...
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154 views

Misleading results with Kruskal-Wallis + Posthoc Test

Dataset: Rows are cross validation sets and columns are different regression methods. The dataset contains RMS error values on a benchmark regression problem. So, lower is better. Here is a boxplot ...
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Maximum number of groups in Kruskal Wallis one-way analysis of variance

Is there a maximum number of groups in Kruskal Wallis' one-way ANOVA? I am looking at a data set with 42 separate groups and I am unsure if there would be some sort of issue in running that many ...
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451 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 ...
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73 views

Mann-Whitney or K-W?

I am studying a biomarker in cancer, and I want to know if there are differences related with the location of the cancer (head and neck, lung or cervix). When I do the Kruskall-Wallis test, I find a ...
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131 views

Nested Anova with count (frequency) data

I have a data set that includes count data (# of times a behavior is observed, 4 total behaviors) that has been recorded at 2 research sites, and on multiple individuals at each site. I'm looking for ...
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439 views

Permutation test for two distributions with the same mean but unequal variance

I am using the coin package in R. For two distributions with the same mean but different variance, the test is unable to reject the null hypothesis that the two ...
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Choosing the right test for cell count data and categorical data

I have recorded data from a lot of cells viewed under a microscope, and am now stuck trying to do a useful analysis of it. I have two types of cells (genotype; WT and null), and I treated them with ...
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Can I use the Kruskal-Wallis test for measures on the same animal before and after a treatment has been applied

In my experiment I have 3 treatment groups. Behaviours are scored for each subject (while they are isolated) before and after the treatment is applied. I thought that the Kruskal-Wallis test could ...
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46 views

Do I need a post-hoc test if the statistically significant group is obvious?

For example, when I compared a student population split into four year groups and compiled a bar graph, I could see that the 2nd year students were vastly overrepresented in their responses to that ...
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What tests would be suitable for a survey with mixed question types?

I have done a survey (n=138) on student preferences of homework types. It's my first time attempting anything of the sort and I have a high schooler's understanding of math and statistics. My null ...