SAS vs. WinNonlin: different sequence effect results [Software]
Dear all,
I have recently analysed a simple crossover bioequivalence study in SAS and detected a significant sequence effect (p=0.0425). To verify my results, I have run the same analysis using the WinNonlin Bioequivalence Wizard (WNL v5.1.1). The results of the analysis were completely identical except for the sequence effect which was not significant (p=0.0634).
The Pharsight support claims that this is due to a slightly different model used by the Bioequivalence Wizard and recommended me to read the online help on linear mixed effects modelling.
I can not follow this argumentation, because in my opinion my model specification is the same. Besides I get identical results for all other effects: both my SAS program and the BE Wizard produce the same SS, MS and DF for sequence effect, period effect, treatment effect and subject within sequence, the MSE is identical in both programs and (consequently) also the confidence limits.
The F statistics and the p-values are the same for period effect, treatment effect and subject within sequence.
I have repeated the comparison with other data with the same result, all values identical, but the F statistic of the sequence effect always lower in WNL compared to SAS.
Has any of you ever come across this discrepancy before?
I wonder if somebody could help me to find out if there is a mistake in the Bioequivalence Wizard calculation or if I am simply too stupid to model my data correctly...
Thanks in advance & kind regards,
Eva
I have recently analysed a simple crossover bioequivalence study in SAS and detected a significant sequence effect (p=0.0425). To verify my results, I have run the same analysis using the WinNonlin Bioequivalence Wizard (WNL v5.1.1). The results of the analysis were completely identical except for the sequence effect which was not significant (p=0.0634).
The Pharsight support claims that this is due to a slightly different model used by the Bioequivalence Wizard and recommended me to read the online help on linear mixed effects modelling.
I can not follow this argumentation, because in my opinion my model specification is the same. Besides I get identical results for all other effects: both my SAS program and the BE Wizard produce the same SS, MS and DF for sequence effect, period effect, treatment effect and subject within sequence, the MSE is identical in both programs and (consequently) also the confidence limits.
The F statistics and the p-values are the same for period effect, treatment effect and subject within sequence.
I have repeated the comparison with other data with the same result, all values identical, but the F statistic of the sequence effect always lower in WNL compared to SAS.
Has any of you ever come across this discrepancy before?
I wonder if somebody could help me to find out if there is a mistake in the Bioequivalence Wizard calculation or if I am simply too stupid to model my data correctly...
Thanks in advance & kind regards,
Eva
Complete thread:
- SAS vs. WinNonlin: different sequence effect resultsEva 2008-05-06 14:04 [Software]
- SAS vs. WinNonlin: different sequence effect results Ohlbe 2008-05-06 15:56
- imbalanced design? Helmut 2008-05-06 16:13
- Sample data & results Eva 2008-05-06 17:42
- Error factor Ohlbe 2008-05-06 19:25
- Error tests between/within Helmut 2008-05-06 21:33
- Error tests between/within Helmut 2008-05-07 18:18
- The power to know d_labes 2008-05-08 11:16
- The power to know Helmut 2008-05-08 17:18
- The power to know d_labes 2008-05-09 09:35
- The power to know Nirali 2008-05-09 11:00
- The power to know d_labes 2008-05-16 08:54
- The power to know Nirali 2008-05-09 11:00
- The power to know d_labes 2008-05-09 09:35
- The power to know kevan 2009-05-25 15:46
- Bogus statement for 2,2,2-BE ElMaestro 2009-05-25 22:25
- Bogus? What? d_labes 2009-05-27 08:57
- Linear model on steroids ElMaestro 2009-05-28 19:12
- Bogus? What? d_labes 2009-05-27 08:57
- Fixed nowadays what? d_labes 2009-05-27 09:03
- Bogus statement for 2,2,2-BE ElMaestro 2009-05-25 22:25
- The power to know Helmut 2008-05-08 17:18
- Kinetica 5.0 bug Helmut 2008-12-31 16:42
- Error tests between/within Helmut 2008-05-06 21:33
- Error factor Ohlbe 2008-05-06 19:25
- Sample data & results Eva 2008-05-06 17:42