这是应用统计学的题目:
It is against the law to discriminate against job applicants
on the basis of race, religion, sex, or age.
Of the individuals who apply for a statistcian's position
in a large corporation, 41% are over 45 years of age.
The company decides to choose 46 of a very large number of applicants for
closer screening, claiming that the selection will be random and
not age-biased.
Let x be the number in the sample of 46 who are over 45 years of age.
If you wish to find P(x≦21), the probability that x is at most 21,
what is the z-score associated with this x-value of 21?
(Assume that the applicant pool is large enough so that x has a
binomial probability distribution.)
除了解题过程外，
我想请问解这题是用到什么观念还是方法?
是关于二项分配还是标准常态分配还是其他方法，
因为我解了很久都解不出来，
希望能给我一些指示，谢谢。