Open issues [R for BE/BA]

posted by ElMaestro  – Denmark, 2020-08-06 21:11 (283 d 16:53 ago) – Posting: # 21827
Views: 8,076

(edited by ElMaestro on 2020-08-06 21:23)

Hi PharmCat,

I really like your idea. I don't have a good understanding of this as a whole but I know that when I work with a little these things they become easier for me to grasp, so I am giving it a try. :-)

Let us turn to Gurka 2006 equation 3 and 5 and remembering that the rank of our overall design matrix X is 6:
Gurka requires me to derive Xi, the design matrix for fixed effects of subject i.
They mention that "Xi is a (ni × p) known, constant design matrix for the i' th subject
with rank p"

At just three observations per subject we cannot have a rank of p=6 for Xi. The maximum rank is naturally 3. I don't see a way to handle Xi on a subject by subject basis, but perhaps you have some insight. Possibly I could do it by lumping subjects together so that the "smaller" X of sorts still has more rows thank columns and thus a rank of p=6.

Do you see my issue with Xi? Could you indicate your view on Xi here? Is lumping subjects together a way to go to ensure the right rank of the reduced design matrices? Many thanks in advance.

Pass or fail!

Complete thread:

 Admin contact
21,462 posts in 4,487 threads, 1,514 registered users;
online 18 (0 registered, 18 guests [including 8 identified bots]).
Forum time: Monday 14:04 CEST (Europe/Vienna)

Garbage in, garbage out.
It’s very very simple.    Anders Fuglsang

The Bioequivalence and Bioavailability Forum is hosted by
BEBAC Ing. Helmut Schütz