12k views

Is there an equivalent to Kruskal Wallis one-way test for a two-way model?

If the model does not satisfy ANOVA assumptions (normality in particular), if one-way, Kruskal-Wallis non-parametric test is recommended. But, what if you have multiple factors?
15k views

A non-parametric repeated-measures multi-way Anova in R?

The following question is one of those holy grails for me for some time now, I hope someone might be able to offer a good advice. I wish to perform a non-parametric repeated measures multiway anova ...
8k views

Can I do a t test if I have little to no variance in one group?

I have 4 groups that I am comparing to a criterion. In one of my groups, all the participants answered the same on every item, i.e. there is no variance. How do I deal with that in my ANOVA? Also, ...
12k views

Randomisation/permutation test for paired vectors in R

I'm not an expert, so forgive me if some of the terminology is a little clumsy. Happy to provide more information where required. I have two vectors of 50 paired numeric values in R. I want to ...
8k views

Is there an alternative to the Kolmogorov-Smirnov test for tied data with correction?

I've got a bunch of data from two samples (control and treated), each containing several thousand values which are to undergo significance testing in R. Theoretically, the values should be continuous, ...
18k views

What are some good examples of exploratory data analysis today?

Are there some papers published which illustrate EDA used to tackle substantial data problems? I am particularly looking for actual (current) data examples, where plots have been made and statistics ...
1k views

Is it wrong to jitter before performing Wilcoxon test?

I wrote a script tests the data using the wilcox.test, but when I got the results, all the p-values where equal to 1. I read in some websites that you could use ...
3k views

Student's t vs Mann-Whitney U for small equal samples

I have 2 groups of data to compare using a t-test, both of sample size n=5. Checking to see if the normality assumption of the test holds is difficult since the sample sizes are too small. I have ...
759 views

Subsets not significantly different but superset is

I have various clinical data on participants in a study. I'm looking at a continuous variable ("A") and a (binary) categorical variable (group) ("O"). I used a Wilcoxon test in R (the data are not ...
971 views

Testing difference between two means with pairwise data and absence of normality

I am trying to compare the difference between two means with two pairwise samples. Unfortunately, my data are very far of being normal. What test would you recommend to use in this situation? Should I ...
7k views

When sample size is small and distribution is not normal should I use Wilcoxon or T-test or something else?

I have two sets of data and need to compare mean times for a variety of situations (i.e. time of day, day of the week, different areas, etc...). Some of the situations have small samples sizes (n=8) ...
1k views

Paired permutation test for repeated measures

I have a data set consisting of interactions between male-female dyads within a group in two conditions. The values range from -1 to 1 and indicate how responsible the female was for maintaining the ...
2k views

How to report a permutation test?

I want to compare a parameter between two independent groups of volunteers (see MWE below). All volunteers had baseline reading (V1) and a subsequent reading by a later visit (V2) for intervention (<...
Suppose I perform a paired test. The null hypothesis is that mean of difference is zero: $\mathrm{E[X-Y]} = 0$. The actual difference is positive but distributed non normally. Which statistical ...