单选题
According to the central limit theorem, a sampling distribution of the sample mean will be approximately normal only if:
A、
the sample size is large.
B、
the underlying distribution is normally distributed.
C、
the variance of the underlying distribution is known.
【正确答案】
A
【答案解析】
[解析] 根据中心极限定理，当样本空间n足够大时(n≥30)，样本平均值的抽样分布趋近于正态分布。因此，本题的正确选项为A。
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