题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233152-50336.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233152-42280.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233153-64881.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233152-42280.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233153-25403.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233153-63515.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233153-73992.png)
解析
试题分析:
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233152-42280.png)
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![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233155-67558.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233155-22772.png)
核心考点
试题【小李练习射击,每次击中目标的概率为,用表示小李射击次击中目标的次数,则的均值与方差的值分别是______________________.】;主要考察你对离散型随机变量均值与方差等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233147-80542.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233147-74600.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233148-51952.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233148-66618.png)
(1)求图中x的值;
(2)从成绩不低于80分的学生中随机选取2人,该2人中成绩在90分以上(含90分)的人数记为ξ,求ξ的数学期望.
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233136-12652.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191029/20191029233107-44019.png)
若要在成绩较高的第3,4,5组中用分层抽样抽取6名学生进行复查:
(1)已知学生甲和学生乙的成绩均在第四组,求学生甲和学生乙至少有一人被选中复查的概率;
(2)在已抽取到的6名学生中随机抽取3名学生接受篮球项目的考核,设第三组中有三名学生接受篮球项目的考核,求暑的分布列和数学期望.