All Questions
Tagged with nonparametric hypothesis-testing
54
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
24
votes
5
answers
13k
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What exactly does a non-parametric test accomplish & What do you do with the results?
I have a feeling this may have been asked elsewhere, but not really with the type of basic description I need. I know non-parametric relies on the median instead of the mean to compare... something. ...
- 315
77
votes
15
answers
12k
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Why would parametric statistics ever be preferred over nonparametric?
Can someone explain to me why would anyone choose a parametric over a nonparametric statistical method for hypothesis testing or regression analysis?
In my mind, it's like going for rafting and ...
- 947
52
votes
3
answers
51k
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Bootstrap vs. permutation hypothesis testing
There are several popular resampling techniques, which are often used in practice, such as bootstrapping, permutation test, jackknife, etc. There are numerous articles & books discuss these ...
- 2,957
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
20
votes
3
answers
3k
views
When to check model assumptions
Statistical methods are based on model assumptions. For example, an independent one-way ANOVA makes the following assumptions:
Normally distributed residuals
Homogeneity of variance
Independence of ...
- 301
22
votes
1
answer
43k
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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
18
votes
5
answers
5k
views
Checking ANOVA assumptions
A few months ago I posted a question about homoscedasticity tests in R on SO, and Ian Fellows answered that (I'll paraphrase his answer very loosely):
Homoscedasticity tests are not a good tool ...
- 2,211
9
votes
5
answers
8k
views
Wilcoxon Signed Rank Symmetry Assumption
The assumption of symmetricity for signed rank test (and its relevance) is becoming extremely confusing for me. I am hypothesizing that sub-population A (before treatment) and sub-population B (after ...
- 93
13
votes
1
answer
12k
views
Friedman test vs Wilcoxon test
I'm trying to assess performance of a supervised machine learning classification algorithm. The observations fall into nominal classes (2 for the time being, however I'd like to generalize this to ...
- 233
28
votes
2
answers
19k
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Non-parametric test if two samples are drawn from the same distribution
I would like to test the hypothesis that two samples are drawn from the same population, without making any assumptions about the distributions of the samples or the population. How should I do this?
...
- 467
19
votes
3
answers
2k
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Statistical test for two distributions where only 5-number summary is known?
I have two distributions where only the 5-number summary (minimum, 1st quartile, median, 3rd quartile, maximum) and sample size are known. Contrary to the question here, not all data points are ...
- 1,095
6
votes
1
answer
9k
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Friedman's test and post-hoc analysis
I am carrying out a statistical analysis for my research. I am using a Friedman's test with post hoc analysis. At present I am using the function ...
- 61
6
votes
2
answers
3k
views
How to compare two non-normally distributed samples with very different sizes? (Mann-Whitney vs Randomization/Bootstrap)
Perhaps this is a very basic question, but I didn't find yet a simple solution for this simple problem:
I want to compare two samples (say X and Y) for a continuous variable which is non-normally ...
- 75
4
votes
3
answers
6k
views
non-parametric two-sample equivalence tests with unequal sample sizes
I would like to compare means/medians of two samples that may be very skewed in size, e.g. 25 points and 1 or 2 points and test them for similarity, rather than difference. I realize that the power ...
- 473