## 2 Groups model FDA [Two-Stage / GS Designs]

Gents!

» » But honestly, group x treatment?? I'd rather not go down that road. I hope you do not make precedence.
»
» Not my invention. See this post for the reference.

I have another 'better' one (from a Letter of FDA, Barbara M. Davit)!

" ... the following statistical model should be used when analyzing data from a multiple group bioequivalence study:

Group Sequence Treatment Subject(nested within Group*Sequence) Period(nested within Group) Group-by-Sequence Interaction (sic!) Group-by-Treatment Interaction

Subject(nested within Group*Sequence) is a random effect and all other factors are fixed effects. ..."

Enormous effect(s) .

BTW: Helmut, how had you planned the evaluation of the second stage, if it would be necessary?

BTW2: In context of a 2-Stage design, also a 2-group design with groups here called stage, the mighty oracle prohibit us the Group-by-Treatment Interaction! From the EMA Q&A Rev.7 :
"Conclusion ... A term for a formulation*stage interaction should not be fitted."

BTW3: NOL = no objection letter ?

Regards,

Detlew