terminology [Power / Sample Size]

posted by Helmut Homepage – Vienna, Austria, 2017-08-04 14:41 (2427 d 22:06 ago) – Posting: # 17664
Views: 18,501

Hi Darya,

❝ You are wrote about converting the standard deviation to СV, but use the formula to convert the standard error to СV. I thought that the standard deviation and standard error are different parameters.


Like in this thread it is a question of terminology; see this thread for details.
In PowerTOST type ?se2CV to get the formulas for conversion. If you want a second opinion:1

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Nitpick: Chaos everywhere. We have only sw – which is the estimate of the unknown σw
BTW, when it comes to reference-scaling, both the EMA and the FDA correctly use swR. Since scaling is based on the unknown parameters, we might observe an inflation of the type I error.2


  1. Patterson S, Jones B. Bioequivalence and Statistics in Clinical Pharmacology. Boca Raton: Chapman & Hall / CRC; 2nd ed. 2016: p.47.
  2. Labes D, Schütz H. Inflation of Type I Error in the Evaluation of Scaled Average Bioequivalence, and a Method for its Control. Pharm Res. 2016;33(11):2805–14. doi:10.1007/s11095-016-2006-1. full text view-only.

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