求X的数学期望EX和方差DX.

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问题 求X的数学期望EX和方差DX.

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答案EX=0×0.2+1×0.1+2×0.3+3×0.4 =1.9 DX=(0-1.9)2×0.2+(1-1.9)2×0.1+(2-1.9)2×0.3+(3-1.9)2×0.4 =1.29

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