I have been told I cannot have a fold change of less than 1. Is this correct? I want to describe the fold change for the following: 62 (original value) to 64 (final value). I have calculated 62/64 = 0.97. Should this in fact be 1.03?
It is customary to use final / original when computing fold change. But there is nothing wrong with a fold change < 1.
Because "change" signifies difference to some, less confusing nomenclature would be one of the following:
- post:pre ratio
- ratio of post to pre
- effect ratio
- post/pre (my favorite)