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mathews ● 2008-01-31 11:59 (6307 d 07:27 ago) Posting: # 1568 Views: 7,764 |
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Hi All, Please clariffy my doubt regarding the analysis of a BE study with unequal sequences. For a 2 x 2 BE study of total 24 subjects with two sequences AB and BA.i.e, 12 subjects with sequence AB and 12 with sequence BA. But in the end of the study one subject in the sequence AB is dropped out.So 11 subjects with seq AB and 12 subjects with seq BA. Is there any problem if I analyse this unbalanced data using a usual GLM procedure in SAS.? or go for a MIXED procedure in SAS?. Any diffence in the output? Regards Matz |
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Helmut ★★★   Vienna, Austria, 2008-01-31 13:40 (6307 d 05:46 ago) @ mathews Posting: # 1569 Views: 6,693 |
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Dear Matz! ❝ For a 2 x 2 BE study of total 24 subjects with two sequences AB and BA. […] one subject in the sequence AB is dropped out. So 11 subjects with seq AB and 12 subjects with seq BA. ❝ Is there any problem if I analyse this unbalanced data using a usual GLM procedure in SAS.? No. ❝ or go for a MIXED procedure in SAS?. Why? PROC MIXED makes only sense for designs with >2 periods (Williams’ designs, replicate designs). ❝ Any difference in the output? Generally no; but for a 2×2 design I would stick to PROC GLM, because PROC MIXED is an iterative procedure (i.e., very small differences may exist). A final remark: the more unbalanced any study gets, the more biased the PE (point estimate) based on the geometric mean ratio gets (the confidence interval remains unaffected). I would recommend using the MVUE (Minimum-variance unbiased estimator) instead - for SAS-code see: S-C Chow and J-p Liu Design and Analysis of Bioavailability and Bioequivalence Studies Marcel Dekker, New York (2nd ed. 2000) The PE is of importance in sample size planning for follow-up studies - the BE assessment is based on the CI only. — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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mathews ● 2008-01-31 13:57 (6307 d 05:29 ago) @ Helmut Posting: # 1570 Views: 6,142 |
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Dear HS, Thanks for your reply.  In the sample size calculation for the follow up studies the PE is used as delta value? Is it right? Regards Matz |
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Helmut ★★★ Vienna, Austria, 2008-01-31 14:08 (6307 d 05:18 ago) @ mathews Posting: # 1571 Views: 6,220 |
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Dear Matz, ❝ In the sample size calculation for the follow up studies the PE is used as delta value? Is it right? Yes, but most software use the PE directly (not the delta: delta=1-PE for PE<1 and delta=PE-1 for PE>1). — Dif-tor heh smusma 🖖🏼 Довге життя Україна! Helmut Schütz The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
Ing. Helmut Schütz