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. Author manuscript; available in PMC: 2013 Mar 7.
Published in final edited form as: Psychol Methods. 2011 Jun;16(2):116–126. doi: 10.1037/a0022657
 dfM1<-10 # degrees of freedom of M1
 dfM2<-12 # degrees of freedom of M2
 delta1<-dfM2*.033ˆ2 # define delta* in the alternative hypothesis
 delta2<-dfM2*.064ˆ2 # define delta** in the alternative hypothesis
 alpha<-.05
 for (n in 1:100000) {
  cv<-qchisq(1-alpha,df=dfM2-dfM1,ncp=n*delta1) # Critical value under H0
  power<-1-pchisq(cv,df=dfM2-dfM1,ncp=n*delta2)
  if (power>=.80) break # reach the desirable power
 }
 N<-n+1
 print(N)