n<-c(10,100,1000,1000)
par(mfrow=c(2,2))

for (i in 1:length(n)){
a<-rbinom(n[i],1000,.5)
b<-rnorm(n[i],500,sd(a))

hist(a, col=rgb(1,0,0,0.4),xlim=c(400,600), main="Overlapping Histogram", xlab="Variable")
hist(b, col=rgb(0,0,1,0.4), add=T)
}