Suppose that eight families live on the same floor of a building and five
of them own their homes and three of them rent. If four families are to be
chosen at random without replacement to form a sample and if X is the
random variable representing the number of homeowners in the sample:
a) what are the possible values of X?
b) what is the probability of getting two homeowners in the sample?
c) what is the probability of getting fewer than two families who rent
their home in the sample?
我唔係好知用咩公式計~
p.s.我係數學白痴~請詳細解釋~thanks~
probabilities question
2010-05-27 12:14 am
回答 (2)
2010-05-27 1:01 am
✔ 最佳答案
a) Since there are 5 homeowners , at most 4 homeowners are to bechosen ; 3 of them rent , at least 1 homeowners .
X = 4 or 3 or 2 or 1
b)
P(getting two homeowners in the sample)
= P(any 2 homeowners from 5 and any 2 rent from 3)
= (5C2 * 3C2) / 8C4
= 3/7
c)
P( fewer than two families who rent)
= P(any 3 homeowners from 5 and any 1 rent) + P(any 4 homeowners from 5 )
= (5C3 * 3C1 + 5C4) / 8C4
= 1/2
2010-05-26 19:55:15 補充：
nCr = 從n個中抽r個的方法數
計算公式 :
nCr = n! / (r! (n-r)!)
其中 n! = 1 x 2 x 3 x...x n
2010-05-27 3:31 am
HI "↗"雨後陽光"↘",
可唔可以quote 埋你用邊條公式去計?
因為我唔係好明~thanks~
數學白痴虫虫
可唔可以quote 埋你用邊條公式去計?
因為我唔係好明~thanks~
數學白痴虫虫
收錄日期: 2021-04-21 22:18:18
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100526000051KK00695