2020年高考前第二次适应性训练结束后,某校对全市的英语成绩进行统计,发现英语成绩的频率分布直方图形状与正态分布的密度曲线
非常拟合.已知
,则方差为_________ .据此估计,在全市随机抽取10名高三同学,设
表示10名同学中英语成绩超过95分的人数,
的数学期望是__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dba744e13fa7cf9a2ba7160e90c46064.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6215c5c0b2ccf0b7bff7b2597a1d94e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f022950e0faa45b617d497b01b5292b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f022950e0faa45b617d497b01b5292b9.png)
更新时间:2021-07-26 06:36:05
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解题方法
【推荐1】如果随机变量
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9607b72ae51053b6e5ac9d96ca72108c.png)
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【推荐2】若随机变量
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ff819e439a3c0cd3e62a8acbdacf1ef.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee81ac855d5754f3adc2079042218e5b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/773c149f40ee5acd389470a074d61662.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ff819e439a3c0cd3e62a8acbdacf1ef.png)
您最近一年使用:0次
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【推荐1】若随机变量ξ的概率分布密度函数是
,x∈R,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/541515ea36d8219981dbf5b4690767e1.png)
__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15bf1c85e2ecd24bff49cb5bb65a8434.png)
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【推荐2】关于标准正态分布
的概率密度函数
的说法中:
①
为偶函数;②
的最大值是
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③
在
时是单调递减函数,在
时是单调递增函数;
④
关于
对称.
正确说法的编号有__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcadfe766e5ce650c693bb394fb7473d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/de3c6a38214737deb77eb5c22f29fdd8.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d89167dd92528d4cefc3671704a8d215.png)
③
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08115d6d9f876dea921a4d32260ff1fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/db2b74d89854116e411c089d053df053.png)
④
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b384412acba251d87902ab928902f16.png)
正确说法的编号有
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