function [m, v] = clt_hist(n)
 x = random('exp', 1, 1, 1000000);
 mean(x)
 var(x)
hist(x, 100);

for i = 2: n
    y = random('exp', 1, 1, 1000000);
    x = x - mean(x) + (y - mean(y));
end
S = x/sqrt(n);
m = mean(S);
v = var(S);
figure; hist(S,100);

