clc
close
num=46000;
step=23000;
n=num/step;

arr=randn(num,1) * 8.239027791394347 + 70;

std(arr)
mean(arr)

arr_s=sort(arr);
s=zeros(step,n);
std_arr=zeros(step,1);
mean_arr=zeros(step,1);

for i=1:n
    a=(i-1)*step +1;
    b=i*step;
    s(:,i)=arr_s(a:b);
    std_arr(i)=std(s(:,i));
    mean_arr(i)=mean(s(:,i));
end
grid on
subplot(2,1,1)
plot(mean_arr)
subplot(2,1,2)
plot(std_arr)