Linked Questions
77 questions linked to/from How to choose between t-test or non-parametric test e.g. Wilcoxon in small samples
26
votes
2
answers
36k
views
When to use the Wilcoxon rank-sum test instead of the unpaired t-test?
This is a followup question to what Frank Harrell wrote here:
In my experience the required sample size for the t distribution to be
accurate is often larger than the sample size at hand. The ...
- 20.6k
15
votes
3
answers
5k
views
Why is the asymptotic relative efficiency of the Wilcoxon test $3/\pi$ compared to Student's t-test for normally distributed data?
It is well-known that the asymptotic relative efficiency (ARE) of the Wilcoxon signed rank test is $\frac{3}{\pi} \approx 0.955$ compared to Student's t-test, if the data are drawn from a normally ...
- 21.7k
20
votes
4
answers
8k
views
Is there any statistical test that is parametric and non-parametric?
Is there any statistical test that is parametric and non-parametric?
This question was asked by an interview panel. Is it valid question?
- 1,929
10
votes
3
answers
24k
views
How can you test homogeneity of variance of two groups with different sample sizes?
I have two groups of data that have different sample sizes and in order to be able to analyze both sets they must have the same variance. I was told I should use Bartlett's to test the homogeneity of ...
- 235
13
votes
2
answers
16k
views
Bartlett's test vs Levene's test
I am currently trying to address violations to ANOVA assumptions. I have used Shapiro-Wilk to test normality, and have dabbled with both Levene's test and Bartlett's test of variance equality. I have ...
- 131
11
votes
1
answer
28k
views
How to choose between sign test and Wilcoxon signed-rank test?
I am trying to pick one from these two tests to analyze paired data. Does anyone know any rules of thumb about which one to pick in general?
- 377
4
votes
1
answer
34k
views
Normality, and when to use t-test vs. Mann-Whitney U-test?
I am looking for a few rules of thumb of when to determine that my data is 'normal enough' to use a t-test vs. a Mann-Whitney U-test.
From what I have read, most real world data sets are non-normal, ...
- 45
4
votes
4
answers
5k
views
Both t-test and F-test are significant, do I report both?
I undertook a large study (N about 200 in both control and treatment) in which one of the user ratings is significantly different (p < 0.0001). When I ran the unpaired t-test, the F-test also ...
- 293
9
votes
1
answer
5k
views
Relative efficiency of Wilcoxon signed rank in small samples
I have seen in published literature (and posted on here) that the asymptotic relative efficiency of the Wilcoxon signed rank test is at least 0.864 when compared to the t test. I have also heard that ...
- 1,173
3
votes
3
answers
1k
views
importance of CLT in t-test and z-test
I was going through the assumptions of z-test and t-test, all most all of the references mention that the data should be normally distributed. There is no mention of estimator's distribution. If the ...
- 87
3
votes
2
answers
21k
views
Comparing z-scores from different data sets
Is it possible to use z-score as a number to compare two different data sets (none of them with normal distribution) and identify which one has an average z-score higher than another? Thanks!
- 31
6
votes
2
answers
1k
views
Does testing for assumptions affect type I error?
I just performed simple simulation. Made two "populations" with different means and the same variance. Since I prepared them I know that they: are normal, differs in location and both have the same ...
- 205
4
votes
2
answers
7k
views
t test with log transformation
One of my variables to be compared in a t-test is normally distributed, while the other is non-normally distributed. What test should I use? I thought I should do a reflect log10 transformation on the ...
- 77
6
votes
2
answers
6k
views
Q-Q plot and sample size
To study the quantile-quantile plot, I used the following codes (modified from here). The first group of pictures is derived from 100 data points while the second from 10000.
...
- 1,296
4
votes
3
answers
4k
views
How to interpret histogram and normaltest result?
I investigated dataset using histogram and normaltest. I used scipy.stats.normaltest, got this result:
...
- 43