Hello everyone,
I have research including two objectives,
one of them is to assess the relationship using logistic regression.
another one is comparing two groups using Mann-Whitney U Test.
if I want to apply sample size formulation need to calculate separately for each objective?
also what is the Minium sample size for logistic?
Thanks.
What software do you typically use?
Re logistic regression, do you want to estimate the sample size needed to detect an effect of a given size? Or are you thinking about rules of thumb concerning events-per-variable (to reduce the likelihood of overfitting)?
Here are some resources that may be helpful.
- https://www.researchgate.net/post/How-to-calculate-sample-sizes-for-multiple-logistic-regression
- https://stats.stackexchange.com/questions/162294/multiple-logistic-regression-power-analysis
- https://discourse.datamethods.org/t/author-checklist/3407#arrow_rightoverfitting-and-lack-of-model-validation-26
- https://cran.r-project.org/web/packages/wmwpow/wmwpow.pdf
Thank you for the response, I use SAS to run the analysis and PASS to run the sample size.
I have two objectives for this research. One requires logistics, and the other requires the Mann-Whitney U Test to compare two groups.
My issue is, should I have a separate sample size for each goal? I think it is common to have one sample size for whole the research.
Thank you for clarifying, Bahar Ysr. PASS has routines for both logistic regression and the Wilcoxon-Mann-Whitney test. So I would estimate the needed sample sizes for both and then choose the larger of the two.
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