Linked Questions

-1
votes
1answer
816 views

When should one use the Welch's T-test? [duplicate]

I want to test whether the mean in two samples are different. I don't know their variance and estimate them from the sample. When should I use the Welch-Satterthwaite approximation to the degrees of ...
0
votes
0answers
105 views

Welch t-test: Exactly when should it be used? [duplicate]

The guidance on this site concerning when to use the Welch t-test is somewhat general in nature (When conducting a t-test why would one prefer to assume (or test for) equal variances rather than ...
92
votes
7answers
75k 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 ...
38
votes
8answers
19k views

How to test hypothesis of no group differences?

Imagine you have a study with two groups (e.g., males and females) looking at a numeric dependent variable (e.g., intelligence test scores) and you have the hypothesis that there are no group ...
19
votes
4answers
9k views

Practically speaking, how do people handle ANOVA when the data doesn't quite meet assumptions?

This isn't a strictly stats question--I can read all the textbooks about ANOVA assumptions--I'm trying to figure out how actual working analysts handle data that doesn't quite meet the assumptions. I'...
17
votes
4answers
7k views

Robust t-test for mean

I am trying to test the null $E[X] = 0$, against the local alternative $E[X] > 0$, for a random variable $X$, subject to mild to medium skew and kurtosis of the random variable. Following ...
13
votes
3answers
726 views

Choosing a statistical test based on the outcome of another (e.g. normality)

So I have heard it said that it is not a good idea to choose one statistical test based on the outcome of another. This seems strange to me though. For example, people often choose to use a non ...
4
votes
4answers
4k 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 ...
5
votes
2answers
3k views

What exactly does scipy.stats.ttest_ind test?

From the description: "This is a two-sided test for the null hypothesis that 2 independent samples have identical average (expected) values." Taken literally, this seems to be saying that we're ...
3
votes
1answer
408 views

How does the Welch correction for the t-test make the test non-parametric?

In an answer to another question it is asserted that the Welch correction to the t-test makes it non-parametric, and this assertion isn't challenged by a frequent contributor with a deep level of ...
0
votes
1answer
428 views

When to test for homoscedasticity?

Under what condition(s) do I need to test for homoscedasticity (i.e. using the Levene's test)? Is this only for repeated-measure designs or do I need to test for this in independent designs as well?