Bioequivalence and Bioavailability Forum

❝ The greater the number of fixed effects, the greater the difference between REML and ML.

REML is an approach that produces unbiased estimators for some special cases and produces less biased estimates than ML in general. Some people say that REML is unbiased. It is like denominators N and N-1 for variance if you have data from all general population - you can use ML, when you have a small part of population - you should use REML. If you have many independent observations (over 200 for example) then estimates will be nearly same. Some info.