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【单选题】
若随机变量 x 服从正态分布 N(μ σ 2 ) , x 1 、 x 2 、 ... 、 x n 是由 x 总体得来的随机样本,则样本平均数 也是一个随机变量,其总体均值和方差分别是( )。A.
μ和σ 2
B.
μ/n和σ 2 /n
C.
μ/n和σ 2
D.
μ和σ 2 /n
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offend
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