random effect, fix effect in the guidance Appendix E [Regulatives / Guidelines]

posted by LS – 2008-02-05 19:53 (5918 d 16:35 ago) – Posting: # 1589
Views: 18,546

Hi,
For average BE analysis of replicated crossover studies, the following SAS code is from Guidance for Industry 'Statistical Approaches to Establishing Bioequivalence', January 2001, Appendix E

PROC MIXED;
CLASSES SEQ SUBJ PER TRT;
MODEL Y=SEQ PER TRT/DDFM=SATTERTH;
RANDOM TRT/TYPE=FA0(2) SUB=SUBJ G;
REPEATED/GRP=TRT SUB=SUBJ;
ESTIMATE 'T vs. R' TRT 1-1/CL ALPHA=0.1;

Does anybody know which why TRT is written in random effect and also in fixed effect. Why TRT is random effect? What description is correct to address statistical method from the above code

Thanks

LS

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