设X₁,X₂,...,X₆为来自总体X的样本,且X~N(0,1),则D(X₁²+X₂²+...+X₆²)=().
设X₁,X₂,...,X₆为来自总体X的样本,且X~N(0,1),则D(X₁²+X₂²+...+X₆²)=().
【正确答案】:12
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