The programmes offered by a community college are open to all enrollments without any special entrance requirements. Past records indicate that 7 out of 10 of the participants would drop out before completing the enrolled programmes. Twenty participants are randomly selected from the list of all enrolled participants. What is the probability that:
(a) exactly 5 out of these 20 participants would complete their enrolled programmes in the college? (5 marks)
(b) 10 or more of these 20 participants would complete their enrolled programmes in the college? ( 7marks )
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2010-12-05 5:17 am
回答 (2)
2010-12-05 8:11 am
✔ 最佳答案
------------------------------------------------------------------------------------------------------------圖片參考：http://img256.imageshack.us/img256/5913/probability1.png
2010-12-05 00:11:40 補充：
http://img256.imageshack.us/img256/5913/probability1.png
2010-12-05 6:33 am
(a) Combination: nCr = 20C5 = 15504
P(complete) = 3/10
P(incomplete) = 7/10
(3/10)^5 x (7/10)^15 x nCr
=0.00243 x 0.004747561 x 15504
=0.1789
(b) Combination: nCr = 20C10 184756
=(3/10)^10 x (7/10)^10 x nCr
=0.0308
P(complete) = 3/10
P(incomplete) = 7/10
(3/10)^5 x (7/10)^15 x nCr
=0.00243 x 0.004747561 x 15504
=0.1789
(b) Combination: nCr = 20C10 184756
=(3/10)^10 x (7/10)^10 x nCr
=0.0308
收錄日期: 2021-04-13 17:41:48
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20101204000051KK01398