An exerxise contains 9 question,A teacher assigns 3 question to students.
a) A student igrones the teacher's instruction and answer 5 questions randomly. Find the probability that will answer
i) all 3 questions assigned by the teacher
ii) only one question assigned by the teacher.
probability?
2016-11-03 1:02 pm
回答 (2)
2016-11-03 1:07 pm
✔ 最佳答案
就是用我上次教你分組考慮的方法啊！［這種分布其實叫 hypergeometric distribution 超幾何分布，但當然中學生不必理會太深入的細節。］
9 questions:
＊Group 1: 3 questions being assigned
＊Group 2: 6 questions not assigned
(a) (i)
The probability that the 5 answered questions involve all the assigned questions is
[3C3 × 6C2]/(9C5)
= 1 × 15 / 126
= 15/126
= 5/42
(a) (ii)
The probability that the 5 answered questions involve only one of the assigned questions is
[3C1 × 6C4]/(9C5)
= 3 × 15 / 126
= 45/126
= 5/14
2016-11-08 3:15 am
Total no. of possible permutations of questions:5P3=60
i answer: 5/60=1/12
ii answer: 3x3/60=9/20
i answer: 5/60=1/12
ii answer: 3x3/60=9/20
收錄日期: 2021-04-18 15:45:44
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20161103050201AAGjJsm