period x sequence [Design Issues]

posted by d_labes  – Berlin, Germany, 2016-12-21 10:45 (1858 d 11:45 ago) – Posting: # 16869
Views: 7,087

Dear ElMaestro,

» » Is it possible to determine the interaction between period and sequence effect?
»
» Yes. It is a treatment effect.
» E.g. Period 1 in (or x) Sequence TR is effectively just treatment T (in that period). Note that some serious DF elimination may come into play depending on how you specify the model. For example, in the model matrix the columns for "period 1 in Seq TR" and "period 2 in Seq RT" will add up to exactly the column for the Treatment T effect. If you have the interaction before the treatment in your model spec, then the latter will get a type I SS and MS of zero.

IMHO your description is totally correct.

But my judgment to Johns question would be different:
No. Its not possible to to determine the interaction between period and sequence effect and the treatment effect in a classical 2x2 crossover. Both terms are confounded.
It's the same situation if you try to determine a carry-over effect and a direct sequence effect simultaneously.

Regards,

Detlew

Complete thread:

Activity
 Admin contact
21,835 posts in 4,569 threads, 1,554 registered users;
online 9 (0 registered, 9 guests [including 7 identified bots]).
Forum time: Saturday 22:30 CET (Europe/Vienna)

Science may set limits to knowledge,
but should not set limits to imagination.    Bertrand Russell

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