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RegisterSample size, alpha, beta, beta/2 and that all [General Statistics]
Dear Astea,
don't fiddle too much with the formulas given by Chow, Wang and who ever co-authors. There are many typing errors or hidden, not explained assumptions in the mentioned paper and book.
IMHO the only correct way to estimate the sample size is 'brute force', i.e. choose a sample size, estimate power and than iterate sample size until desired power is reached.
All other ways are more or less approximations to tackle the problem avoiding the not so easy power calculations. But in the ages where PowerTOST is available there is no need for such approximations
.
These attempts are only useful for obtaining a reasonable start value for 'brute force'. As such they are used within PowerTOST.
Have a look at
to get the formulas used (including z1-ß or z1-ß/2 and such things).
don't fiddle too much with the formulas given by Chow, Wang and who ever co-authors. There are many typing errors or hidden, not explained assumptions in the mentioned paper and book.
IMHO the only correct way to estimate the sample size is 'brute force', i.e. choose a sample size, estimate power and than iterate sample size until desired power is reached.
All other ways are more or less approximations to tackle the problem avoiding the not so easy power calculations. But in the ages where PowerTOST is available there is no need for such approximations
. These attempts are only useful for obtaining a reasonable start value for 'brute force'. As such they are used within PowerTOST.
Have a look at
Paul Zhang (2003)
"A Simple Formula for Sample Size Calculation in Equivalence Studies"
Journal of Biopharmaceutical Statistics, 13:3, 529-538
to get the formulas used (including z1-ß or z1-ß/2 and such things).
—
Regards,
Detlew
Regards,
Detlew
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Ing. Helmut Schütz