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RegisterPowerTOST sample size FDA full replicate T/R ratio at 85% [🇷 for BE/BA]
Dear Shuange!
The why is not so easy to answer. It is a result of a complex interplay of the dependence of the linearized RSABE criterion from GMR and CVwR and of the additional point estimate constraint. My suggestion: Take the observed effect as is
.
"Not widened yet" is the false. Think from the underlying method - simulation of studies with true CV and true GMR = theta0. And think further in terms of widened acceptance limits:
If we simulate with CV=30% we have realizations where the implied acceptance limits are wider and others where the conventional acceptance limits have to be used. The probability of both studies is 0.5. If we go to smaller CV's the proportion with wider implied acceptance limits decreases. For higher CV's we get more studies with wider implied acceptance limits.
So far so good. This doesn't imply that at CV=30% the sample size is highest since we have the point estimate constraint in effect. This leads to the shift of the maximum sample size downwards of 30%. This is also the case for your calculations with theta0=0.9, but not so pronounced seen as with theta0=0.85. Check it by power calculations with n=120 for theta0=0.85 or theta0=0.9 and n=32. You will find the minimum (implying max. sample size) below CV=30% in both cases.
Of course not! Even the suspicion is an injury
!
It must be correct because PowerTOST says so.
Count up: post 995
❝ Why is that?
The why is not so easy to answer. It is a result of a complex interplay of the dependence of the linearized RSABE criterion from GMR and CVwR and of the additional point estimate constraint. My suggestion: Take the observed effect as is
.❝ Since all other assumptions are same (e.g., T/R ratio is still 85%), when ISCV increased from e.g., 28% to 29% and 30%, shouldn't we need more subjects as the BE criteria is not widened yet?
"Not widened yet" is the false. Think from the underlying method - simulation of studies with true CV and true GMR = theta0. And think further in terms of widened acceptance limits:
If we simulate with CV=30% we have realizations where the implied acceptance limits are wider and others where the conventional acceptance limits have to be used. The probability of both studies is 0.5. If we go to smaller CV's the proportion with wider implied acceptance limits decreases. For higher CV's we get more studies with wider implied acceptance limits.
So far so good. This doesn't imply that at CV=30% the sample size is highest since we have the point estimate constraint in effect. This leads to the shift of the maximum sample size downwards of 30%. This is also the case for your calculations with theta0=0.9, but not so pronounced seen as with theta0=0.85. Check it by power calculations with n=120 for theta0=0.85 or theta0=0.9 and n=32. You will find the minimum (implying max. sample size) below CV=30% in both cases.
❝ If my understanding is correct, then maybe it's a bug of the package?
Of course not! Even the suspicion is an injury
! It must be correct because PowerTOST says so
.Count up: post 995
—
Regards,
Detlew
Regards,
Detlew
Complete thread:
- PowerTOST sample size FDA full replicate T/R ratio at 85% Shuanghe 2016-01-25 17:49 [🇷 for BE/BA]
![[Mix]](https://static.bebac.at/img/mix.png "open in Mix view")
- PowerTOST sample size FDA full replicate T/R ratio at 85%d_labes 2016-01-26 12:05
- PowerTOST sample size FDA full replicate T/R ratio at 85% Shuanghe 2016-01-26 12:55
- PowerTOST sample size FDA full replicate T/R ratio at 85% d_labes 2016-01-26 14:07
- maximum sample size at which CV? Helmut 2016-01-26 16:31
- maximum sample size at which CV? nobody 2016-01-26 17:40
- maximum sample size at which CV? d_labes 2016-01-27 08:41
- maximum sample size at which CV? nobody 2016-01-27 09:08
- OT: Stop - think -act d_labes 2016-01-27 09:31
- maximum sample size at which CV? nobody 2016-01-27 09:08
- maximum sample size at which CV? Shuanghe 2016-01-28 12:44
- target power 90% Helmut 2016-01-28 13:49
- PowerTOST update d_labes 2016-02-01 19:16
- #1,000 Helmut 2016-02-01 21:49
- OT: post #1,000 d_labes 2016-02-02 21:17
- #1,000 ElMaestro 2016-02-03 16:32
- #1,000 Helmut 2016-02-03 16:50
- OT: #1,000 d_labes 2016-02-05 15:50
- OT: #1,000 ElMaestro 2016-02-05 17:02
- OT: #1,000 d_labes 2016-02-05 19:48
- OT: #1,000 ElMaestro 2016-02-06 15:45
- OT: #1,000 nobody 2016-02-07 09:50
- OT: #1,000 ElMaestro 2016-02-06 15:45
- OT: #1,000 d_labes 2016-02-05 19:48
- OT: #1,000 ElMaestro 2016-02-05 17:02
- #1,000 Helmut 2016-02-01 21:49
- PowerTOST update d_labes 2016-02-01 19:16
- target power 90% Helmut 2016-01-28 13:49
- PowerTOST sample size FDA full replicate T/R ratio at 85% Shuanghe 2016-01-26 12:55
- PowerTOST sample size FDA full replicate T/R ratio at 85%d_labes 2016-01-26 12:05
Ing. Helmut Schütz