x=[16.9 14.3 17.6 16.5 15.5 17 15.9];
x=x-mean(x); 
s=sum1(x);             %求差方和，sum1為求平方和函數(shù)
s0=0.8;
xx=s/s0^2              %統(tǒng)計(jì)量
chi2inv(1-0.05/2,6)    %卡方分布的臨界值，置信度為95%
chi2inv(0.05/2,6)