Bioequivalence and Bioavailability Forum

Hi Mikkabel,

❝ Once the statistical analysis performed, I observed that for the comparison between T1 and T3 and between T2 and T4, the number of degrees of freedom for the fixed effect "period" is 2 instead of 3 (which is the case for the other comparisons).

Not unexpected. I suggest to use the ‘Two-at-a-Time’ approach (see this post, the vignette of PowerTOST, and this article).

❝ Furthermore, "Not estimable" is mentioned in the output of Winonlin.

As usual. In SAS you’ll get a period or zero (not sure).

❝ For information, the statistical analysis was performed using ANOVA model (or equivalent parametric method) with fixed effects usually sequence, subject within sequence, period and formulation.

OK.

❝ To be honest, I don't know how to fix it…

You can’t fix it, sorry.

❝ … and I don't know how to interpret this.

Good question, next question.

❝ Could you please inform me if it is an issue related to the software (Winonlin) or is it related to the model used?

The latter. AFAIK, you will see it in any software.

❝ Additionally, could you explain me how to interpret these results and what should be the impact on the results obtained form the analysis?

Use them as they are.
If you have a lot of stamina see a lengthy thread starting here and another one there.