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   设总体 X 服从正态分布 ex_1257338668872_0.gif σ2 未知。若样本容量 n 和置信水平 1-α 均不变,则对于不同的样本观测值,总体均值 μ 的区间估计的精确度     )。

单选题
2021-07-18 00:08
A、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 12pt; mso-bidi-font-family: ; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">无法确定</span>
B、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 12pt; mso-bidi-font-family: ; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">不变</span>
C、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 12pt; mso-bidi-font-family: ; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">变高</span>
D、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 12pt; mso-bidi-font-family: ; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">变低</span>
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正确答案
B

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