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設:這一組數據共n個數,記為x1,x2,x3,……,xn由題知,∑(xi)²;=228n,∑(xi)=15n而方差σ²;=∑(xi-15)²;/n=[∑(xi)²;-30∑(xi)+15²;∑1]/n=[228n-30*15n+15²;*n]/n=3(以上,∑中的i滿足i=1,2,3…
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