名校
1 . 某单位有
名职工,通过抽验筛查一种疾病的患者.假设患疾病的人在当地人群中的比例为
.专家建议随机地按
(
且为
的正因数)人一组分组,然后将各组
个人的血样混合再化验. 如果混管血样呈阴性,说明这
个人全部阴性;如果混管血样呈阳性,说明其中至少有一人的血样呈阳性,就需要对每个人再分别化验一次.设该种方法需要化验的总次数为
.
(1)当
时,求
的取值范围并解释其实际意义;
(2)现对混管血样逐一化验,至化验出阳性样本时停止,最多化验
次.记
为混管的化验次数,当
足够大时,证明:
;
(3)根据经验预测本次检测时个人患病的概率
,当
时,按照
计算得混管数量
的期望
;某次检验中
,试判断个人患病的概率为
是否合理.(如果
,则说明假设不合理).
附:若
,则
,
,
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/250629ad29d377f3d3ab229dd328d027.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29c8578f06897aa6fb84aa95c797d3d8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc329b32ecf0f0532d09a8a21343e8cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/250629ad29d377f3d3ab229dd328d027.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f022950e0faa45b617d497b01b5292b9.png)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59d23b2cf8ebf243293af6e316925d2f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1010846eeec6c9da29640f5aa3f8738.png)
(2)现对混管血样逐一化验,至化验出阳性样本时停止,最多化验
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4aa0df7f1e45f9de29e802c7f19a4f64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91edc7e2d4811f5ea6c01284cf00393a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4aa0df7f1e45f9de29e802c7f19a4f64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b481119a43237e40b4ab19b59ec27dce.png)
(3)根据经验预测本次检测时个人患病的概率
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3606c4a853a6a34cb7f33bea81b15a1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d31251aec52e0833858cb3041ffb2120.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3606c4a853a6a34cb7f33bea81b15a1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a829fdd8ec0f3b7ede883cf2c3e53b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11f369ea461908186cb8342816785e37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/40ff1f527ec44d057dac7ad8b86d79bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3606c4a853a6a34cb7f33bea81b15a1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/52663ed54c9167744ad6ed29dd2b07d1.png)
附:若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1290917c2c835b61384480b335cc1d13.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93446343720ebe5e94cffd4c15683c4c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4831218b03a6b79a839352bf6b037463.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15bc7b9f904e37882539ded1d462008e.png)
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