n = [5 10 20 30];
k=500;
mu = 8.25;sigma=0.75;
for i = 1:4
 X = normrnd(mu,sigma,n(i),k);
 m = mean(X);
 subplot(2,2,i);
 hist(m);
 axis([6.5 10 0 150]);
 str = sprintf('n= %d',n(i));
 title(str);
end
