%wina
sigma =1.2;
N=60;
me=9.3;
va=0.9;
alfa=1-va;
p_crit=norminv(1-alfa/2)
mean_crit=p_crit*sigma/sqrt(N)
[me - mean_crit, me + mean_crit]
n=100000
x=mean(sigma*randn(N,n))+me;
prctile(x,[5 95])