Bioequivalence and Bioavailability Forum • Proc Mixed FA0(1) for partial replicate

Proc Mixed FA0(1) for partial replicate [RSABE / ABEL]

posted by Wolfgang – Switzerland, 2013-08-06 10:35 (3915 d 05:42 ago) – Posting: # 11219
Views: 8,767

❝ I would think that V (=ZGZ^t+R) should look like this:

❝ – the variance of an R observation is s²_b,R+s²_w,R

❝ …

❝ – optional: the covariance of a mixed observation is "q", which expresses a correlation of the between-sigmas.

❝

❝ No?

Hello ElMaestro,
this is correct although the last line should be: covariance of an R and T observation is s_b,R*s_b,T*q, if q is the correlation.
However, this is the parameterization used with type=CSH, which FDA suggests as an alternative to type=FA0(2).
The two models are equivalent, if you identify a² with s²_b,R, b²+c² with s²_b,T, q with b/sqrt(b²+c²), X with s²_w,R, Y with s²_w,T.
When the design is partially replicated, s²_b,T and s²_w,T cannot be estimated, only their sum can be, leading to overspecification and convergence problems.
With this notation, the remedy would formally be equivalent to setting q=1 – but this is more difficult to justify, and also I would not know how to specify it in SAS.
So I guess we have to stick to FA0(1) and the corresponding notation.

Complete thread:

RSAB model overspecified Wolfgang 2013-08-05 14:37 [RSABE / ABEL]
- RSAB model overspecified jag009 2013-08-05 15:35
- Proc Mixed FA0(1) for partial replicate d_labes 2013-08-05 15:59
  - Proc Mixed FA0(1) for partial replicate Wolfgang 2013-08-05 16:24
    - Proc Mixed FA0(1) for partial replicate ElMaestro 2013-08-05 17:19
      - Proc Mixed FA0(1) for partial replicateWolfgang 2013-08-06 08:35
        
        Proc Mixed FA0(1) for partial replicate ElMaestro 2013-08-06 10:34
    - Proc Mixed FA0(1) for partial replicate d_labes 2013-08-06 10:30
      - FA0(1) for partial replicate in Phoenix Helmut 2013-08-07 15:13
        
        FA0(1) for partial replicate in SAS d_labes 2013-08-08 09:42
        FA0(1) for partial replicate in Phoenix lhughes 2013-08-30 15:17
        
        FA0(1) in PHX: works (& more questions) Helmut 2013-08-30 17:07