搜题请搜索小程序“爱下问搜题”
问题 问答题

设在某一时间段内进入某大型超市的顾客人数X服从参数为A的泊松分布，且每一顾客购买A种商品的概率为p，假定各顾客是否购买A种商品是相互独立的，求进入该超市的顾客购买A种商品的人数Y的概率分布及Y的期望EY。

答案

参考答案：由题设知，[*]
购买A种商品的人数Y，在进入超市的人数X=m的条件下，服从二项分布B(m，p)，即
[*]
由全概率公式有
[*]
又因为当m＜k时，P{Y=k|X=m}=0，所以
[*]
由此可知，Y服从参数为λp的泊松分布，故 EY=λp。

解析：[*]

单项选择题

An Indian anthropologist, Chandra Thapar, made a study of foreign cultures, which had customs similar to (91) of his native land. One culture in (92) fascinated him because it reveres one animal (93) sacred, much as the people in India (94) the cow. The things he discovered might interest you (95) you will be studying India as part of this course.
The tribe Dr. Thapar (96) is called the Asu and is found on the American continent north of the Tamhumara of Mexico. Though it seems to be a (97) developed society of its type, it has an overwhelming (98) with the care and feeding of the rac—an animal much like a bull in size, strength and temperament. In the Asu tribe, it is almost a social (99) to own at least one (100) not more rats. People not possessing at least one are (101) in low esteem by the community because they are too poor to (102) one of these beasts properly. Some members of the tribe, to (103) their wealth and social prestige, even own (104) of racs.
(105) the rac breed is not very healthy and usually does not live more than five to seven years. Each family invests large (106) of money each year to keep its rac healthy and shod, for it has a tendency to throw its shoes often. There are rac (107) in each community, perhaps more than one if the community is particularly (108) . These specialists, however, due to the long period of ritual training they must undergo and (109) the difficulty of obtaining the right selection of charms to treat the rac, demand (110) offerings whenever a family must treat an ailing rac.

A．deal

B．sum

C．sums

D．deals
查看答案
问答题 简答题

双母线接线方式下，差动保护动作使母线停电应如何处理？
查看答案