tmpar <- par(mar=c(4,.5,.5,.5),mfcol=c(3,1))

hist(ran,nclass=20,yaxt="n",xlab="")
mtext("(a) responses",1,2,at=mean(par("usr")[1:2]),cex=1)
hist(apply(ran,2,mean),nclass=20,yaxt="n",xlab="")
mtext("(b) class means",1,2,at=mean(par("usr")[1:2]),cex=1)
hist(apply(ran,2,function(x){x-mean(x)}),nclass=20,yaxt="n",
   xlab="")
mtext("(c) element residuals",1,2,at=mean(par("usr")[1:2]),cex=1)

par(tmpar)