Bingo! [Two-Stage / GS Designs]
now you got it!
❝ – the alpha2 that works for n2,min=2 or 0 or 1 or whatever is not necessarily the alpha2 that works for n2,min=1.5*n1, all other factors being equal.
Yes.
❝ It is tempting to say power increases with sample size, and since type I error is a kind of power, this is the logic behind the observation.
Yes.
❝ I think the issue is somewhat more complex than just that. These two-stage thingies are funny objects that defy all kinds of logic.
Maybe and yes.
❝ Does it change anything though??
For me, no.
❝ I mean you and I both argued in the past that universally functional alpha's do not exist, so whenever someone makes a smart/clever/sophisticated/dumb/intelligent/braindead amendment to Potvin B or C etc, then simulations should always be undertaken to make sure the type I error is not compromised.
Exactly. To quote Jones and Kenward.*
[…] before using any of the methods […], their operating characteristics should be evaluated for a range of values of n1, CV and true ratio of means that are of interest, in order to decide if the Type I error rate is controlled, the power is adequate and the potential maximum total sample size is not too great.
(my emphases)- Jones B, Kenward MG. Design and analysis of cross-over trials. Boca Raton: Chapman & Hall/CRC; 2014. p. 365–80.
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 Error Helmut 2016-12-30 01:22
- 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