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
  • ratio
  • effect ratio
  • post/pre (my favorite)
  • $\begingroup$ Thank you very much for taking the time to provide and clear and helpful response. $\endgroup$ – N_D81 Jul 29 '15 at 15:06

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