GMR = fixed! [Two-Stage / GS Designs]
Hi BE-proff,
Let me answer for our ol’ Capt’n: The GMR in the estimation of interim power (stage 1) and in the sample size estimation for the second stage is fixed (and not the observed one).
Nope. The observed one can be anything. For Potvin’s B and C it is 0.95 (or 1/0.95 if you prefer). Other methods use other fixed GMRs (the A in my figures below). Look them up in the publications (AFAIK, only methods with 0.95 and 0.90 are published).
For most methods 0.95. If you already expect a “bad” GMR, you could opt for Montague’s or one of Anders’ methods which use a fixed GMR of 0.90 (or 1/0.90). Alternatively you could work with one of the methods with a futility criterion (stopping in stage 1).
Only fully adaptive methods (e.g., by Karalis and Macheras) would use the observed GMR 1.19. See my paper mentioned below why this might not be a good idea…*
❝ What do you mean under controlled GMR […]
Let me answer for our ol’ Capt’n: The GMR in the estimation of interim power (stage 1) and in the sample size estimation for the second stage is fixed (and not the observed one).
❝ - being within 0.95-1.05? Correct?
Nope. The observed one can be anything. For Potvin’s B and C it is 0.95 (or 1/0.95 if you prefer). Other methods use other fixed GMRs (the A in my figures below). Look them up in the publications (AFAIK, only methods with 0.95 and 0.90 are published).
❝ So, if 1 stage of any method shows GMR 1.19 which figure shoud be taken for 2 stage: 0.95 or 1.19
For most methods 0.95. If you already expect a “bad” GMR, you could opt for Montague’s or one of Anders’ methods which use a fixed GMR of 0.90 (or 1/0.90). Alternatively you could work with one of the methods with a futility criterion (stopping in stage 1).
Only fully adaptive methods (e.g., by Karalis and Macheras) would use the observed GMR 1.19. See my paper mentioned below why this might not be a good idea…*
- For beginners… Of course, the original methods can be tweaked in such a way that the power is sufficient. But that requires exhaustive simulations.
—
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Dif-tor heh smusma 🖖🏼 Довге життя Україна!
![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png)
Helmut Schütz
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The quality of responses received is directly proportional to the quality of the question asked. 🚮
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Complete thread:
- Data for 2nd stage of Potvin’s designs BE-proff 2017-02-18 06:40 [Two-Stage / GS Designs]
- Data for 2nd stage of Potvin’s designs ElMaestro 2017-02-18 10:20
- Data for 2nd stage of Potvin’s designs BE-proff 2017-02-18 13:29
- GMR = fixed!Helmut 2017-02-18 16:23
- Data for 2nd stage of Potvin’s designs BE-proff 2017-02-18 13:29
- “Type 1” slightly higher power than “Type 2” for the same adj. α Helmut 2017-02-18 11:51
- “Type 1” slightly higher power than “Type 2” for the same adj. α BE-proff 2017-02-18 13:31
- Terminology Helmut 2017-02-18 16:27
- Terminology Yura 2017-02-20 11:28
- Which GMR to plug in ElMaestro 2017-02-20 11:46
- Which GMR to plug in BE-proff 2017-02-21 11:35
- Which GMR to plug in ElMaestro 2017-02-21 11:47
- Which GMR to plug in BE-proff 2017-02-21 11:35
- Validated frameworks; observed GMR not relevant Helmut 2017-02-22 12:03
- Validated frameworks; observed GMR not relevant Silva 2017-03-09 01:26
- GMR, theta 0 and that all d_labes 2017-03-09 09:21
- GMR, theta 0 and that all Silva 2017-03-09 12:38
- GMR, theta 0 and that all ElMaestro 2017-03-09 12:56
- GMR, theta0 and that all d_labes 2017-03-09 13:55
- GMR, theta0 and that all Silva 2017-03-09 18:01
- GMR, theta 0 and that all Silva 2017-03-09 12:38
- GMR, theta 0 and that all d_labes 2017-03-09 09:21
- Validated frameworks; observed GMR not relevant Silva 2017-03-09 01:26
- Which GMR to plug in ElMaestro 2017-02-20 11:46
- Terminology Yura 2017-02-20 11:28
- Terminology Helmut 2017-02-18 16:27
- “Type 1” slightly higher power than “Type 2” for the same adj. α BE-proff 2017-02-21 11:31
- “Type 1” slightly higher power than “Type 2” for the same adj. α BE-proff 2017-02-18 13:31
- Data for 2nd stage of Potvin’s designs ElMaestro 2017-02-18 10:20