Hi; Is there any faster way to run this code : ## b0, beta.r and stud are already defined. Ab<- matrix(numeric(1),nrow=2,ncol=1000) Bb<- matrix(numeric(1),nrow=2,ncol=1000) for( j in 1:1000) { for(i in 1:1000) { eq<- sample(stud,replace=T) ystar<- beta.r*x+eq+b0 Ab[,i]<- wwfit(x,ystar)$coef } Bb[1,j]<-sd(Ab[1,]) Bb[2,j]<-sd(Ab[2,]) } se1<- mean(Bb[1,]) se2<- mean(Bb[2,]) se1 se2 thanks alot for your help. Rebhi Bsharat. dept of stat KSU. __________________________________________________ [[alternative HTML version deleted]]