No random effects in ANOVA [General Sta­tis­tics]

posted by Helmut Homepage – Vienna, Austria, 2020-02-04 11:33 2a02:8388:6bc2:ce80:59da:2536:a4ac:85cd – Posting: # 21142
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Hi Abhimanyu,

» Generally we mention this sentence in Bio-equivalence protocol "ANOVA model will include Sequence, Formulation and Period as fixed effects and Subject (Sequence) as a random effect. Sequence effect will be tested using Subject (Sequence) as error term."
»
» Why we take "Subject (Sequence) as a random effect??":confused:

Simple:

Because you copypasted this part from one protocol to the other and it is also mentioned in most (all?) guidelines. ;-)


Seriously:Whether subjects should be treated as a fixed or random effect is almost a philosophical question. In the strict sense:
  1. If you specify subjects as a fixed effect in the model, you make a statement about the subjects in the study.
  2. If you specify them as a random effect, you make a statement about the population of other subjects.
At the end of the day you extrapolate results of the study to the population of patients.
Some statisticians (including ones of the FDA, Health Canada, China’s CDE, and myself) think that (b) is the correct way. Others (of the EMA, …) prefer (a). If the study is balanced and complete (i.e., no missing periods) the outcome is identical.

Cheers,
Helmut Schütz
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