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

Hi John,

» 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.

That's what I meant. By FDA's code, all subject has to complete all 4 periods. so In practice, number of subjects having T data is always equal number of to subjects having R data.

By the way, I asked FDA about possibility of modify the code to include subject with 2 R and 1 T and for "ilat", the mean difference between T and R, use the modified version:
ilat = lat1t - 0.5*(lat1r+lat2r) ,
where lat1t could be replaced by lat2t depending on period of dropout. It should be easy to implement with IF/ELSE/THEN. Buy they confirmed 1 and a half years later that subjects should have data of all 4 periods and reject the suggestion.

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

Woo, long post! I'll definitely take a look at them later. Thanks.

All the best,
Shuanghe

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