Sample Size II [Power / Sample Size]

posted by BE-proff – 2016-12-28 09:14 (2647 d 05:49 ago) – Posting: # 16892
Views: 9,122

Hi All,

Let's say I want to calculate sample size based on results of a previous study.

I have the following data:
n=20
CV=0.18 (for Cmax and AUC) ;-)
GMR1 = 0.97
GMR2=1.19

If to calculate size based on GMR1 I think it's better to use a script:

sampleN.TOST(CV=0.18, theta0=0.95)

+++++++++++ Equivalence test - TOST +++++++++++
            Sample size estimation
-----------------------------------------------
Study design:  2x2 crossover
log-transformed data (multiplicative model)

alpha = 0.05, target power = 0.8
BE margins = 0.8 ... 1.25
True ratio = 0.95,  CV = 0.18

Sample size (total)
 n     power
16   0.820357
:ok:

if to use GMR = 1.19 we see something terrible:

sampleN.TOST(CV=0.18, theta0=1.19)

+++++++++++ Equivalence test - TOST +++++++++++
            Sample size estimation
-----------------------------------------------
Study design:  2x2 crossover
log-transformed data (multiplicative model)

alpha = 0.05, target power = 0.8
BE margins = 0.8 ... 1.25
True ratio = 1.19,  CV = 0.18

Sample size (total)
 n     power
166   0.803570
- too many people...:no:

What to do in such situations?:confused:

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