Trouble with powerreg

[barthr]

Dear list

I would like to use powerreg for determining the appropriate sample size for a multiple regression model. The module works when only one predictor is in the model, but when specifying multiple predictors, as in:

powerreg, r2f(0.3) rfr(0.25) nvar(7) ntest(7) power(.80)

I receive the error message:

option nn() invalid

Any information would be greatly appreciated to resolve this problem.

I am using Stata 12 SE.

Barth

[wbuchanan]

You could set up a simulation study instead. There's a fairly old article in the Stata Journal (http://www.stata-journal.com/sjpdf.h...iclenum=st0010) that explains how to do so, as well as a more recent example from one of the Stata User Group Conferences http://www.stata.com/meeting/new-orl...3-luedicke.pdf.

[Paul T Seed]

Your example has a typo. It should be

powerreg, r2f(0.3) r2r(0.25) nvar(7) ntest(7) power(.80)

However, to get your quoted error message (or something like it), I need a different typo:

. powerreg, r2f(0.3) r2r(0.25) nn(7) ntest(7) power(.80)
option nn() not allowed
r(198);

[barthr]

Thanks Paul! That did the trick!

Barth