V [🇷 for BE/BA]

posted by ElMaestro  – Denmark, 2011-01-28 13:14 (5204 d 00:56 ago) – Posting: # 6507
Views: 66,721

Dear d_labes,

❝ where are the intra-individual (error or residual) variances or sd for Test and Reference?

❝ You have only one residual.

❝ The trt1 and trt2 variances (and corr) in your output are the between subject covariance parameter.


Interesting. Let us discuss for a moment the covariance matrix V (not Z and not G, and at this point also not discussing which syntax SAS applies for the given problem (leaves disussions about CSH, FA(0) out here)).
V holds the key.
Further, let us assume for simplicity we only look at the first subject which is the first 4x4 of V where the data are ordered as TRTR (i.e. per1-per2-per3-per4 for the first subject; in the original dataset above they were ordered differently but the order in this context does not change the point):

Data in per1 and per3 correlate within the subject as (s)he gets T (within variance VT).
Data in per2 and per4 correlate within the subject as (s)he gets R (within variance VR).
To this we add a common error variance on the diagonal (V0).

Having no particular mathematical understanding, the first 4x4 of V I think will be:
V0+VT     0         VT       0
0         V0+VR     0        VR
VT        0         V0+VT    0
0         VR        0        V0+VR

Both of the models discussed above correspond to a fit with this V, as far as I can see.
—
Pass or fail!
ElMaestro

Complete thread:

UA Flag
Activity
 Admin contact
23,424 posts in 4,927 threads, 1,672 registered users;
77 visitors (0 registered, 77 guests [including 4 identified bots]).
Forum time: 15:10 CEST (Europe/Vienna)

There are two possible outcomes: if the result confirms the
hypothesis, then you’ve made a measurement. If the result is
contrary to the hypothesis, then you’ve made a discovery.    Enrico Fermi

The Bioequivalence and Bioavailability Forum is hosted by
BEBAC Ing. Helmut Schütz
HTML5