Hi friends,
I am about to perform a ssc (sample size calculation) with transformed continuous data, of which I have (still will have) an untransformed mean and an untransformed sd. The untransformed values are between 0 and 100. I can easily transform the mean and the reference value, but how do I transform the sd before putting them into an ssc? The applied transformation is [x=untransformed, y=transformed]:
Y=TAN((X-50)*PI/100.001)+X-50
This way, dividing by 100.001) x-values of 0 and 100 will have existing, but extreme transformed values, unequal to minus or plus infinite.
Regards - Jim.
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Jim Groeneveld, MSc.
Biostatistician
Science Team
Vitatron B.V.
Meander 1051
6825 MJ Arnhem
P.O.Box 5227
6802 EE Arnhem
the Netherlands
Tel: +31/0 26 376 7365
Fax: +31/0 26 376 7305
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