# Without any normalization and transformation, is the default LM equivalent to a parametric t-test?

**URL:** <https://forum.biobakery.org/t/without-any-normalization-and-transformation-is-the-default-lm-equivalent-to-a-parametric-t-test/2816>\
**Category:** MaAsLin\
**Created:** [November 20, 2021, 2:58am UTC](https://forum.biobakery.org/t/without-any-normalization-and-transformation-is-the-default-lm-equivalent-to-a-parametric-t-test/2816 "2021-11-20T02:58:42Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ruizzhan](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@ruizzhan](https://forum.biobakery.org/u/ruizzhan)\
**Post date:** [November 20, 2021, 2:58am UTC](https://forum.biobakery.org/t/without-any-normalization-and-transformation-is-the-default-lm-equivalent-to-a-parametric-t-test/2816/1 "2021-11-20T02:58:42Z")

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Dear MaAsLin2 developer,

This might be a very silly question, I’ve been trying to understand how does MaAsLin2 work statistically, but as indicated in the title, if I don’t perform any normalization and transformation, and I only have 1 level of categorical variables to compare, the default linear model would just compare each variable with the reference using a linear model, which essentially makes it a parametric t-test, does this make sense? please correct me if I am wrong. In such a case, would MsAsLin2 tests for the assumptions of parametric tests before reporting the statistical conclusions?

Thank you!

Rui

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**Author:** ![Kelsey\_Thompson](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.biobakery.org/kelsey_thompson/32/65_2.png) [@Kelsey\_Thompson](https://forum.biobakery.org/u/Kelsey_Thompson)\
**Post date:** [December 6, 2021, 1:01pm UTC](https://forum.biobakery.org/t/without-any-normalization-and-transformation-is-the-default-lm-equivalent-to-a-parametric-t-test/2816/2 "2021-12-06T13:01:32Z")

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Hi @ruizzhan,

Thanks for your question! To my understanding - if you perform no normalization or transformation (not recommended with MaAsLin) - yes these two tests would be essentially the same. Specifically, in this case, the test you are specifying, I believe, simplifies to a two-sample t-test with equal variance assumption.

I hope this helps.  
Best,  
Kelsey

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**Author:** ![ruizzhan](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@ruizzhan](https://forum.biobakery.org/u/ruizzhan)\
**Post date:** [December 7, 2021, 1:57am UTC](https://forum.biobakery.org/t/without-any-normalization-and-transformation-is-the-default-lm-equivalent-to-a-parametric-t-test/2816/3 "2021-12-07T01:57:48Z")

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Thank you for the clarification!