All Questions
Tagged with nonparametric t-test
96
questions
140
votes
8
answers
121k
views
How to choose between t-test or non-parametric test e.g. Wilcoxon in small samples
Certain hypotheses can be tested using Student's t-test (maybe using Welch's correction for unequal variances in the two-sample case), or by a non-parametric test like the Wilcoxon paired signed rank ...
- 23.8k
63
votes
7
answers
54k
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Which permutation test implementation in R to use instead of t-tests (paired and non-paired)?
I have data from an experiment that I analyzed using t-tests. The dependent variable is interval scaled and the data are either unpaired (i.e., 2 groups) or paired (i.e., within-subjects).
E.g. (...
- 14.3k
22
votes
1
answer
43k
views
Should I use t-test on highly skewed data ? Scientific proof, please?
I have samples from a highly skewed (looking like an exponential distribution) dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want ...
- 551
8
votes
3
answers
46k
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What is a minimum sample size for a paired t-test and what is a non-parametric equivalent if data is non-normal?
I have 4 sample pairs, let's say (x1, y1),...,(x4, y4).
What is the minimum sample size for a paired t-test?
Which assumption should I check for paired t-test?
If my data is non-normal, what is an ...
- 1,284
7
votes
3
answers
9k
views
Non-parametric alternative to simple t-test
I have five numeric variables of two populations (each of them with 60 individuals) and for each of those five variables I want to know if there is difference in the means.
I was trying to use a ...
7
votes
4
answers
9k
views
Should I use t-test on highly skewed and discrete data?
I have samples from a highly skewed dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want to compare their mean. For that, I'm using ...
- 551
7
votes
2
answers
12k
views
Non-Parametric altervative to one sample t-test
I have a the following hypothesis: $H_0: \mu=4$, $H_1: \mu\neq 4$, which I wanted to test using a one sample t-test.
However, my data is not normally distributed and a transformation was not found. ...
- 486
7
votes
1
answer
2k
views
Use of Wilcoxon test for non-normal data akin to Two One Sided T-test
I'm analysing paired data for equivalency and it's not normally distributed, i.e., the difference of the paired result is not normally distributed due to, amongst other things, outliers. If it were ...
- 149
6
votes
1
answer
19k
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 ...
- 213
6
votes
3
answers
351
views
T-tests provide info about the margin of mean difference?
I have 2 unpaired datasets where the difference of the sample means is quite substantial (with the naked eye). The t-test shows that the difference is significant (p-value=0.007) and I would like to ...
- 63
6
votes
1
answer
21k
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Non-parametric version of paired t-test (Mann–Whitney U test)
I have data from 100 individuals doing a 2AFC under a control and a manipulated setting. I want to compare the means. I initially used a paired t-test. My supervisor noticed the distributions were not ...
- 582
6
votes
1
answer
3k
views
What differentiates the wilcoxon test from t test regarding ordinal variables?
I'm wondering what the wilcoxon test differentiates from the t test so it can be used with ordinal variables. In other words why can't we use a t test for ordinal variables but can we use a wilcoxon ...
- 753
6
votes
3
answers
5k
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Comparison of medians in samples with unequal variance, size and shape
What am I trying to do and how does my data look?
I am trying to perform some comparisons of medians of groups of data that, most often than not, are not-normally distributed. In some cases I am ...
- 421
6
votes
2
answers
370
views
What is an example of data where the permutation test succeeds but a normal t-test fails?
In literature, I normally see authors use a two sample permutation test on normal data to show that it works as well as the two sample t-test. However, the real power for permutation tests should be ...
- 2,107
5
votes
2
answers
9k
views
Paired t-test of medians
I need to run an inferential test on some large data where the individual data points have a heavily skewed distribution. I'm considering doing a paired t-test across a number of days comparing the ...
- 51