I am trying to detect differentially abundant species based on body location (for ex: face vs arm vs neck).
Just a simplied example of what I am encountering:
If I choose face as the reference, let’s say I see 2 species different between face and arm and 4 between face and neck. Next, I switch to neck as the reference, for some reason, I may get 2 different between neck and face. This is confusing to me because when I chose face as the reference, I saw 4 different species. Why is this number changing? Is it something to do with the reference chosen? What is the “true” value?