2
$\begingroup$

From here and here I see that we cannot use Mann-Whitney test if symmetry assumption is violated. Which test(s) can we use instead of Mann-Whitney test for non-parametric continues data if symmetry assumption is violated? I want to compare two continues independent variables which are non-normally distributed which violates the assumption for t-test. Null hypothesis: median/mean (depending on which of them the test can for test; I think median is better in that case) of one group is similar to another. Alternative hypothesis: median/mean of groups are different.

I do not have actual data yet. I may have it soon and I need to be prepared in case I will not be able to use Mann-Whitney test if symmetry assumption is violated.

Improve this question
$\endgroup$
12
  • 1
    $\begingroup$ What are you actually testing? What are your null and alternative hypotheses? $\endgroup$
    – jbowman
    Jan 14, 2020 at 18:16
  • $\begingroup$ @jbowman Added that information to question. $\endgroup$
    – vasili111
    Jan 14, 2020 at 18:32
  • 2
    $\begingroup$ "Non-parametric" can be a property of a probability model but it's not a characteristic of a variable. If you would like reasonable advice, then please supply some information about (a) the empirical distributions of these variables and (b) the null hypothesis you wish to test. $\endgroup$
    – whuber ♦
    Jan 14, 2020 at 18:35
  • $\begingroup$ @whuber I updated the question and I think now it looks better. If it looks good then please reopen it or please let me know what else can be added. Thank you. $\endgroup$
    – vasili111
    Jan 14, 2020 at 18:45
  • 1
    $\begingroup$ @whuber I do not have actual data yet. I may have it soon and I need to be prepared in case I will not be able to use Mann-Whitney test if symmetry assumption is violated. I understand that you want to make question as best as possible and I really appropriate it (no irony of any kind here). Of course it will be better to add data description to it too but as I said I do not have it and even in this state I think my question is currently valid. $\endgroup$
    – vasili111
    Jan 15, 2020 at 0:31

1 Answer 1

Reset to default
2
$\begingroup$

The Mann-Whitney two-sample test does not require symmetry, and actually the two links that you give don't claim that it does. The first reference addresses the question when Mann-Whitney is a powerful test for equality of medians, but this doesn't mean you can't use it otherwise. The second link doesn't mention the term "symmetry" at all.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.