I've written in last post about two groups of data (case-disease) that need to be compare. This time I don't have binary data but variable data. Example below:
Sample bacteria1 bacteria2 bacteria3 s1 0.5 0.7 0.1 s2 0.03 0.02 0.9 s3 ...
I have 100 samples with disease and 100 samples as control.
To compare the differences between 2 groups (case-control) I've decided to use Mann-Whitney test. But first I would like to predict the sample size for this test with power=0.8 and alpha=0.05. Do you know how can I do that? Is there a tool that can calculate the required sample size for experiment for Mann-Whitney test?
Thanks in advance! Agata