一个总体的平均数和标准差是μ=60，σ=30，P（X＞50)是（不查表)（)A．0.1293B．0.3707C．0.6293D．0

A . u B . t C . F D . χ2

A . ['['1.96σB . 1.96https://assets.asklib.com/psource/2015110815170653471.jpg C .https://assets.asklib.com/psource/2015110815171316604.jpg D .https://assets.asklib.com/psource/2015110815171948972.jpg E . 1.96s

A . A B . B C . C D . D E . E

A . ['['μ+μB . μ-μC .https://assets.asklib.com/psource/2015092210241766887.jpg D .https://assets.asklib.com/psource/2015092210242222800.jpg E .https://assets.asklib.com/psource/2015092210242864305.jpg

A . ['['X1-X2+X3B . 2X3-μC .https://assets.asklib.com/psource/2015101517580884933.jpg D .https://assets.asklib.com/psource/2015101517581233582.jpg E .https://assets.asklib.com/psource/2015101517581652360.jpg

A . μ-1.64σ B . μ+1.64σ C . μ+1.96σ D . μ+2.58σ E . 不能确定

A . 正确 B . 错误

A . u服从正态分布，且均数不变 B . u服从正态分布，且标准差不变 C . u服从正态分布，且均数和标准差都不变 D . u服从正态分布，但均数和标准差都改变 E . u不服从正态分布

A . 均数不变，标准差变 B . 均数和标准差都不变 C . 均数变而标准差不变 D . 均数和标准差都改变 E . 均数与标准差的变化情况无法确定

A . ['1.96Shttps://assets.asklib.com/psource/2015110808370479860.jpg B . 1.96σhttps://assets.asklib.com/psource/2015110808371174628.jpg C .https://assets.asklib.com/psource/2015110808371467487.jpg D .https://assets.asklib.com/psource/2015110808372260476.jpg E .https://assets.asklib.com/psource/2015110808372851270.jpg

A . ['['1.96σB . 1.96σhttps://assets.asklib.com/psource/2015092914183963979.gif C .https://assets.asklib.com/psource/2015092914185355064.gif D .https://assets.asklib.com/psource/2015092914185642036.gif E . 2.58σ

A．正确 B．错误

设从总体X~N(μ,σ²)中抽取容量为18的一个样本,u,σ²未知,求: <img src='https://img2.soutiyun.com/ask/2020-09-30/970332837126071.png' />

设<img src='https://img2.soutiyun.com/ask/2020-10-04/970679542502247.png' />是取自总体X-N(μ, σ²)的一个样本，均值μ未知，方差σ²已知.;为使μ的双侧1-a置信区间长度不超过I,则至少需要多大的样本量才能达到？

A．+5和s+5 B．+5和s C．和s+5 D．和s E．+5和5+s

A、X+4 和s+4 B、X+4 和s C、X和s+4 D、X和s E、X+4 和2+s

设<img src='https://img2.soutiyun.com/ask/2020-10-04/970676527118777.png' />为取自总体X的一个样本,总体X~N(μ, σ²),<img src='https://img2.soutiyun.com/ask/2020-10-04/970676548305989.png' />分别为样本均值和样本方差，求常数k使得<img src='https://img2.soutiyun.com/ask/2020-10-04/970676562899824.png' />。

A. ['['μ+μ B. μ-μ C.<img src='https://img2.soutiyun.com/shangxueba/ask/18432001-18435000/18432204/2015092210241766887.jpg' /> D.<img src='https://img2.soutiyun.com/shangxueba/ask/18432001-18435000/18432204/2015092210242222800.jpg' /> E.<img src='https://img2.soutiyun.com/shangxueba/ask/18432001-18435000/18432204/2015092210242864305.jpg' />