## Would you be so kind answering our questions? [Power / Sample Size]

Hi kms,

» » study planned for 90% power: The chance to obtain a post hoc power of ≥95% is ~35%.

»

» Is it a thumb rule?

No; obtained in

» how it should be calculated?

Once you performed the simulations, use

Adapt the relevant data according to your needs. For CV 0.30, T/R 0.90, and target power 80% you would get only 7.77% in the range 0.95–0.99 and 8.64% ≥0.95.

» Yes, on getting posthoc analysis, i found three aspects what you said:

» After experiment, it came to know that

» 1. CV getting lower

» 2. GMR close to 1

» 3. No dropouts/withdrawls (though prior consideration of 10% dropouts)

Fine. Can you explain to us

» » » Try and ask yourself which question post-hoc power actually answers. Try and formulate it in a very specific sentence.

For the 5

We tried to answer

» » study planned for 90% power: The chance to obtain a post hoc power of ≥95% is ~35%.

»

» Is it a thumb rule?

No; obtained in

*simulations*by the R-code I posted above. There is only one – rather trivial – rule of thumb: The chance to get a*post hoc*power which is*either*lower*or*higher than the target is ~50%.» how it should be calculated?

Once you performed the simulations, use

`cat("Simulated studies with post hoc power \u22650.95:", sprintf("%.2f%%",`

100*length(res[, 3][res[, 3] >= 0.95])/nsims), "\n")

`Simulated studies with post hoc power ≥0.95: 34.97%`

Adapt the relevant data according to your needs. For CV 0.30, T/R 0.90, and target power 80% you would get only 7.77% in the range 0.95–0.99 and 8.64% ≥0.95.

» Yes, on getting posthoc analysis, i found three aspects what you said:

» After experiment, it came to know that

» 1. CV getting lower

» 2. GMR close to 1

» 3. No dropouts/withdrawls (though prior consideration of 10% dropouts)

Fine. Can you explain to us

*why*you performed a “posthoc analysis” at all? What did you want to achieve? To repeat ElMaestro:» » » Try and ask yourself which question post-hoc power actually answers. Try and formulate it in a very specific sentence.

For the 5

^{th}time (already asked #1, #2, #3, #4): An example would help.We tried to answer

*your*questions. It would be nice if you answer*ours*as well.—

Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮

Science Quotes

*Dif-tor heh smusma*🖖Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮

Science Quotes

### Complete thread:

- Power is getting high kms.srinivas 2017-12-26 07:39 [Power / Sample Size]
- 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