## SAS and R (?) for variability comparison (FDA NTID Guidance) [General Sta­tis­tics]

Hi,

» 4. Since FDA request that only subject who complete all 4 periods should be included in the analysis, for obtaining F-distribution value, it seems the degree of freedom vT and vR will always be equal, which is always Ntotal - 2 for full replicate. Right?

Where did you see this? I don't see it in the guidance. However, if you use FDA's SAS code (ie: Progesterone) to extract the variances etc etc, you WILL see that the code only takes subjects who completed both periods for Test and Ref. Example, any subjects who finished only 1T out of 2Ts will be dropped.

Take a look at previous threads involving the Concerta guidance (I started that thread and a few joined in. Sorry I don't have time to set the link now. Need to go party).

Lastly, as to why you get reverse upper and lower limit with the interval, I will try and goof around in SAS next week and see.

John

Edit: The threads John mentioned above: #13991, #14150. [Helmut]