Bioequivalence and Bioavailability Forum

Dear All,

What is the importance of Null ratio (=test/reference) in sample size calculations?

It should be 1 (test/reference=1) or 0.95 or 1.05 (5% variability in test/reference).

I am using paried equivalence test in SAS for sample size calculation where it asked for null ratio. Here I am confused whether to use 1 or 0.95 or to be consider actual variability (geometric mean ratio of test/ref untransformed data) received from the reference/pilot data.

I gone through many guidelines but none has mentioned clearly about null ratio. ANVISA says take difference 0% or 5%. USFDA suggested to consider 5% variability. pls guide what is appropriate?
Is it appropriate to consider actual variability as a null ratio

regards,
Nirali.