名校
解题方法
1 . 为了检测自动流水线生产的食盐质量,检验员每天从生产线上随机抽取.
包食盐,并测量其质量(单位:
).由于存在各种不可控制的因素,任意抽取的一袋食盐的质量与标准质量之间存在一定的误差,已知这条生产线在正常状态下,每包食盐的质量服从正态分布
.假设生产状态正常,记
表示每天抽取的
包食盐中质量在
之外的包数,若
的数学期望
,则
的最小值为( )
附:若随机变量
服从正态分布
,则
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c04e54e0705c5438bf2f4ea7bf67209.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3960d67499df76159982657fe3a1cbca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e84c2c26cbb6b22a415fd0830401aeac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f022950e0faa45b617d497b01b5292b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/33cefd8e989740095c0c6e9b5a42e443.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f022950e0faa45b617d497b01b5292b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7fbe596b72fa7b6bfd1f80e0ee2a5d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
附:若随机变量
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f022950e0faa45b617d497b01b5292b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e84c2c26cbb6b22a415fd0830401aeac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13a1f1910099a6c9d4ceeea0e9420992.png)
A.12 | B.13 | C.14 | D.16 |
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