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RegisterImpact of minimum stage 2 sample size on the Type I Error [Two-Stage / GS Designs]
posted by Helmut 
– Vienna, Austria, 2016-12-30 02:22 (3104 d 20:53 ago) – Posting: # 16908
Views: 8,701
Dear all,
on a recent occasion… We know that the minimum n2 = 2 as required in the Q&A document is meaningless. Either a study stops in the first stage or it continues with at least two subjects anyway.
![[image]](img/uploaded/image406.png)
However, do not go further unless you know what you are doing. If you require a minimum stage 2 sample size all studies where a smaller sample size would already be sufficient to demonstrate BE with the target power are now forced to this size. Higher sample size ⇒ more degrees of freedom ⇒ narrower CI ⇒ higher probability to pass BE.
In other words, the TIE will also increase and one would have to use a lower adjusted α.
To the right an example what would happen if one modifies Potvin’s Methods B and C at the location (n1 12, CV 20%) of the maximum TIE and naïvely applies the ‘natural constant’ α 0.0294.
Not a very good idea. Own simulations are mandatory in order to find a suitable α!
on a recent occasion… We know that the minimum n2 = 2 as required in the Q&A document is meaningless. Either a study stops in the first stage or it continues with at least two subjects anyway.
However, do not go further unless you know what you are doing. If you require a minimum stage 2 sample size all studies where a smaller sample size would already be sufficient to demonstrate BE with the target power are now forced to this size. Higher sample size ⇒ more degrees of freedom ⇒ narrower CI ⇒ higher probability to pass BE.In other words, the TIE will also increase and one would have to use a lower adjusted α.
To the right an example what would happen if one modifies Potvin’s Methods B and C at the location (n1 12, CV 20%) of the maximum TIE and naïvely applies the ‘natural constant’ α 0.0294.
Not a very good idea. Own simulations are mandatory in order to find a suitable α!
—
Dif-tor heh smusma 🖖🏼 Довге життя Україна!![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png)
Helmut Schütz
![[image]](https://static.bebac.at/img/CC by.png)
The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes
Dif-tor heh smusma 🖖🏼 Довге життя Україна!
Helmut Schütz
The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes
Complete thread:
- Impact of minimum stage 2 sample size on the Type I ErrorHelmut 2016-12-30 01:22
![[Mix]](https://static.bebac.at/img/mix.png "open in Mix view")
- Impact of minimum stage 2 sample size on the Type I Error ElMaestro 2016-12-30 12:12
- Impact of minimum stage 2 sample size on the TIE: example Helmut 2016-12-30 14:01
- Impact of minimum stage 2 sample size on the TIE: example ElMaestro 2016-12-30 17:19
- Impact of minimum stage 2 sample size on the TIE: example Helmut 2016-12-30 18:00
- Impact of minimum stage 2 sample size on the TIE: example ElMaestro 2016-12-30 18:50
- Bingo! Helmut 2016-12-30 19:00
- Impact of minimum stage 2 sample size on the TIE: example ElMaestro 2016-12-30 18:50
- Impact of minimum stage 2 sample size on the TIE: example Helmut 2016-12-30 18:00
- Impact of minimum stage 2 sample size on the TIE: example ElMaestro 2016-12-30 17:19
- Impact of minimum stage 2 sample size on the TIE: example Helmut 2016-12-30 14:01
- Impact of minimum stage 2 sample size on the Type I Error ElMaestro 2016-12-30 12:12
Ing. Helmut Schütz