Bioequivalence and Bioavailability Forum • Common variance!

Common variance! [Design Issues]

posted by jag009 – NJ, 2012-06-13 18:08 (4757 d 00:11 ago) – Posting: # 8728
Views: 9,748

Hi Helmut,

❝ ❝ Could I hypothetically strip the two treatments (successful test formulation and the reference) and re-run stats in a two-way crossover fashion to re-evaulate the data?

❝ (my emphasis)

❝

❝ See this goody (slides 60–67). The title ‘Don’t try this at home!’ tells it all. You are not the first one having such an idea (see also here).

Don't fly over the atlantic and hit me with a hammer on this ... I am just hypothesizing

If I do strip the good test and reference arms from such a 4-way crossover study (3 T vs R), assign the 2 treatments to a 2-treatment randomization scheme according to how the two were arranged in the original 4-treatment randomization such as,

A, B, C, D --> assign as A D
B, C, D, A --> assign as D A
C, D, A, B --> assign as D A
B, A, C, D --> assign as A D

I then re-run the stats to show that the test is bioequivalent to the reference. The sample size doesn't change.

Why would the above be "Don't try this at home"?

I ran a simulation last night based the data from a successful 2-way crossover study by:

Adding 2 simulated test arms to artificially inflate and deflate the common variance (the pooled intra CV)
Ran 90% CI to get the results for the "Target" arms.

I reverse the simulation (as in stripping the Target and reference arm) and re-evaulate the study as a 2-way study. The results I got was exactly the same as the original data (the 90% CIs matched).

?

Thanks

John

Complete thread:

Curiosity: Running BE studies with more than 2 arms jag009 2012-06-11 15:01 [Design Issues]
- Common variance! Helmut 2012-06-11 16:23
  - Common variance! jag009 2012-06-11 17:25
    - Common variance! Helmut 2012-06-11 17:35
      - Common variance! jag009 2012-06-11 20:03
        
        Common variance! ElMaestro 2012-06-11 20:34
        
        Common variance! Helmut 2012-06-12 01:03
        
        Common variance! ElMaestro 2012-06-12 13:22
  - Common variance! jag009 2012-06-12 19:56
    - What if I run a study with 2 references? jag009 2012-06-12 20:00
    - Common variance! Helmut 2012-06-12 20:39
      - Two References d_labes 2012-06-13 09:11
        
        Two References jag009 2012-09-10 22:48
        
        Two treatments only d_labes 2012-09-11 08:20
  - Common variance!jag009 2012-06-13 16:08