REPORTING POWER
Statisticians are routinely forced to guess at the values of population parameters to make the power calculations needed to determine sample size. It is tempting, once the data are in hand, to redo these same power calculations. Do and do not.
Do repeat the calculations using the same effect size and variance estimate used originally while correcting for a reduced sample size due to missing data. On the other hand, post-hoc calculations making use of parameter estimates provided by the data invariably inflate the actual power of the test [Zumbo and Hubley, 1998].
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