alghazam
☆    

Jordan,
2021-01-18 22:32
(37 d 04:09 ago)

Posting: # 22181
Views: 337
 

 Group Effect [General Sta­tis­tics]

Dear All,
Previous posts and responses on significance of group effect were focusing on the Group*Treatment factor. What is the situation when group term is associated with a p-value of 0.02 and the treatment*group is associated with a p-value of more than 0.35.


Edit: Category changed; see also this post #1[Helmut]
Helmut
★★★
avatar
Homepage
Vienna, Austria,
2021-01-19 11:32
(36 d 15:08 ago)

@ alghazam
Posting: # 22182
Views: 278
 

 Single site?

Salam alghazam,

» Previous posts and responses on significance of group effect were focusing on the Group*Treatment factor.

Which is crap. See this presentation.

» What is the situation when group term is associated with a p-value of 0.02 …

That’s at least unusual if the the study was performed in multiple groups at one site.
If this was a multi-center study (group = site), it happens more often.

» … and the treatment*group is associated with a p-value of more than 0.35.

Fine, if the study was performed at one site. Acc. to the FDA it will allow you to drop this effect and proceed with ‘Model II’. However, this procedure leads to an inflate Type I Error because you have a pre-test (slides 20–21 of the presentation). Simply use ‘Model II’ with the following effects directly:
  • group,
  • sequence,
  • treatment,
  • subject(group × sequence),
  • period(group), and
  • group-by-sequence interaction.


PS: I will have a meeting with the FDA (dealing with a multi-site study) in the near future. Will report back how they reacted. ;-)

Dif-tor heh smusma 🖖
Helmut Schütz
[image]

The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes
Activity
 Admin contact
21,355 posts in 4,458 threads, 1,493 registered users;
online 3 (0 registered, 3 guests [including 2 identified bots]).
Forum time: Thursday 02:41 CET (Europe/Vienna)

The rise of biometry in this 20th century,
like that of geometry in the 3rd century before Christ,
seems to mark out one of the great ages or critical periods
in the advance of the human understanding.    R.A. Fisher

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