## Yes, but why? [Power / Sample Size]

Hi all,

I think the answer to the first question of this post is "because you were very pessimistic on your assumptions regarding sample size" which is something very common in BABE trials (at least, this is my perception).

In this case, given your simulations above and the expected probability of approximately 12% of the studies having power greater then 95% having in consideration the initial assumptions, post hoc power means nothing. But if you had 100 studies instead and 90% of the had >95% power although the sample size was calculated assuming expected power of 80%, some questions and conclusions might be drawn from those results, don't you think? From my understanding of the initial question, this was the case found. So I think that they should start by reviewing how they define their assumptions for the sample size, namely why they assume GMR=1.10 instead of the "normal" 0.95/1.05.

Regards,

David

I think the answer to the first question of this post is "because you were very pessimistic on your assumptions regarding sample size" which is something very common in BABE trials (at least, this is my perception).

In this case, given your simulations above and the expected probability of approximately 12% of the studies having power greater then 95% having in consideration the initial assumptions, post hoc power means nothing. But if you had 100 studies instead and 90% of the had >95% power although the sample size was calculated assuming expected power of 80%, some questions and conclusions might be drawn from those results, don't you think? From my understanding of the initial question, this was the case found. So I think that they should start by reviewing how they define their assumptions for the sample size, namely why they assume GMR=1.10 instead of the "normal" 0.95/1.05.

Regards,

David

### Complete thread:

- Power is getting high - kms.srinivas, 2017-12-26 07:39
- Power is getting high? - d_labes, 2017-12-26 12:08
- Stop estimating post hoc power! - Helmut, 2017-12-26 12:22
- Stop estimating post hoc power! - kms.srinivas, 2017-12-26 13:00
- Stop estimating post hoc power! - ElMaestro, 2017-12-26 14:11
- Simulations - Helmut, 2017-12-26 15:51
- Simulations - BE-proff, 2017-12-27 06:53
- Simulations - ElMaestro, 2017-12-27 07:25
- Simulations - Yura, 2017-12-27 08:23
- Simulations - kms.srinivas, 2017-12-27 09:11
- Simulations - Yura, 2017-12-27 10:07
- α and 1–β - Helmut, 2017-12-27 12:57
- α and 1–β - Yura, 2017-12-27 13:33
- α and 1–β - Helmut, 2017-12-27 14:31
- α and 1–β - Yura, 2017-12-28 06:50
- Educate the IEC and regulators - Helmut, 2017-12-28 11:30

- α and 1–β - Yura, 2017-12-28 06:50

- α and 1–β - Helmut, 2017-12-27 14:31

- α and 1–β - Yura, 2017-12-27 13:33

- α and 1–β - Helmut, 2017-12-27 12:57
- “Forced BE” 101 - Helmut, 2017-12-27 12:23
- “Forced BE” 101 - kms.srinivas, 2017-12-27 12:41
- Would you be so kind answering our questions? - Helmut, 2017-12-27 13:02
- Would you be so kind answering our questions? - kms.srinivas, 2017-12-28 05:53
- Yes, but why? - Helmut, 2017-12-28 11:47
- Yes, but why? - DavidManteigas, 2017-12-28 16:59
- Optimists and pessimists - Helmut, 2017-12-28 17:33
- "normal" GMR setting - d_labes, 2017-12-28 18:57
- Example for discussion - mittyri, 2017-12-28 22:06
- Example for discussion - Helmut, 2017-12-28 22:33

- I prefer to play it safe - Helmut, 2017-12-28 22:10

- Example for discussion - mittyri, 2017-12-28 22:06

- "normal" GMR setting - d_labes, 2017-12-28 18:57
- Full ACK - d_labes, 2017-12-28 17:41
- About GMR 1.10 - kms.srinivas, 2017-12-29 13:20
- Better 0.95 or 0.90 - Helmut, 2017-12-29 16:18

- Optimists and pessimists - Helmut, 2017-12-28 17:33
- Yes, but why? - Yura, 2017-12-29 13:46
- Buffon's needle - Astea, 2018-01-20 23:55
- Buffon's needle - Oleg777, 2018-10-09 22:48
- 0.95 or 1.05 - Helmut, 2018-10-10 13:41

- Buffon's needle - Helmut, 2018-10-10 12:46
- Buffon's needle - Astea, 2018-10-11 23:14
- School maths - Helmut, 2018-10-12 01:10
- School russian - Astea, 2018-10-12 12:41
- Offtop: Umschrift der westlichen Eigennamen auf Russisch - mittyri, 2018-10-12 23:25

- School maths - Helmut, 2018-10-12 01:10

- Buffon's needle - Astea, 2018-10-11 23:14

- Buffon's needle - Oleg777, 2018-10-09 22:48

- Yes, but why? - DavidManteigas, 2017-12-28 16:59

- Yes, but why? - Helmut, 2017-12-28 11:47
- EEU? - mittyri, 2017-12-28 21:52
- EEU? - Yura, 2017-12-29 13:41
- EEU - pharmacokinetic equation??? - mittyri, 2017-12-29 14:11

- EEU? - Beholder, 2018-01-16 15:10

- EEU? - Yura, 2017-12-29 13:41

- Would you be so kind answering our questions? - kms.srinivas, 2017-12-28 05:53

- Would you be so kind answering our questions? - Helmut, 2017-12-27 13:02

- “Forced BE” 101 - kms.srinivas, 2017-12-27 12:41

- Simulations - Yura, 2017-12-27 10:07

- Simulations - kms.srinivas, 2017-12-27 09:11
- Simulations - xtianbadillo, 2018-01-18 22:22

- Simulations - BE-proff, 2017-12-27 06:53

- Stop estimating post hoc power! - kms.srinivas, 2017-12-26 13:00
- Numbers don't lie - ElMaestro, 2017-12-28 20:13