Hi Folks, I'm looking for a neat procedure for the following: Given t0 such that pt(t0,df,ncp=0) = alpha (given) find ncp0 such that for given beta pt(t0,df,ncp=ncp0) = (1 - beta) (In other words, what's the ncp such that you get power (1-beta) to detect it, using a 1-sided test with size alpha when ncp = 0?) In the past I've done the groping by hand, but this time it needs to be done many times over, so a good solver for ncp0 in this situation would be handy. With thanks, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 26-Apr-05 Time: 15:02:24 ------------------------------ XFMail ------------------------------
(Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> writes:> Hi Folks, > > I'm looking for a neat procedure for the following: > > Given t0 such that > > pt(t0,df,ncp=0) = alpha (given) > > find ncp0 such that for given beta > > pt(t0,df,ncp=ncp0) = (1 - beta) > > (In other words, what's the ncp such that you get power (1-beta) > to detect it, using a 1-sided test with size alpha when ncp = 0?) > > In the past I've done the groping by hand, but this time it > needs to be done many times over, so a good solver for ncp0 > in this situation would be handy.You might want to peek inside power.t.test(). Or just use it... -- O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907