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

posted by Wolfgang – Switzerland, 2013-08-06 08:35  – Posting: # 11219
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» I would think that V (=ZGZt+R) should look like this:
» – the variance of an R observation is s2b,R+s2w,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 sb,R*sb,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 s2b,R, b2+c2 with s2b,T, q with b/sqrt(b2+c2), X with s2w,R, Y with s2w,T.
When the design is partially replicated, s2b,T and s2w,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.

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