Suppose that 85% of all undergraduate students in a university wear glasses. If five undergraduate students are to be randomly selected and X is the random variable representing the number of students wearing glasses among the five:
(a) What are the possible values of X?
(b) What is the probability of having three of the five students wearing glasses?
(c) What is the probability of having at least four of the five students not wearing glasses?
有冇人講我知點計:( 要步驟 thanks !!!!!
急件statisticss (20點)
2012-11-12 10:40 am
回答 (2)
2012-11-12 4:16 pm
✔ 最佳答案
Random Variable is X = No. of students wearing glasses among 5 students.(a) Possible values of X : 0, 1, 2, 3, 4 and 5.
(b) This belongs to a Binomial Distribution, X ~ B(5, 0.85)
P(X = 3) = 5C3( 0.85^3)(1 - 0.85)^2 = 10(0.85^3)(0.15^2) = 0.1382.
(c) P(At least 4 NOT wearing glasses) = P(At most 1 wearing glasses)
= P(X = 0) + P(X = 1) = 5C0(0.85^0)(0.15^5) + 5C1(0.85)(0.15^4)
= 0.0000759 + 0.00215 = 0.0022.
2012-11-15 4:44 am
Random Variable is X = No. of students wearing glasses among 5 students.
(a) Possible values of X : 0, 1, 2, 3, 4 and 5.
(b) This belongs to a Binomial Distribution, X ~ B(5, 0.85)
P(X = 3) = 5C3( 0.85^3)(1 - 0.85)^2 = 10(0.85^3)(0.15^2) = 0.1382.
(c) P(At least 4 NOT wearing glasses) = P(At most 1 wearing glasses)
= P(X = 0) + P(X = 1) = 5C0(0.85^0)(0.15^5) + 5C1(0.85)(0.15^4)
= 0.0000759 + 0.00215 = 0.0022
(a) Possible values of X : 0, 1, 2, 3, 4 and 5.
(b) This belongs to a Binomial Distribution, X ~ B(5, 0.85)
P(X = 3) = 5C3( 0.85^3)(1 - 0.85)^2 = 10(0.85^3)(0.15^2) = 0.1382.
(c) P(At least 4 NOT wearing glasses) = P(At most 1 wearing glasses)
= P(X = 0) + P(X = 1) = 5C0(0.85^0)(0.15^5) + 5C1(0.85)(0.15^4)
= 0.0000759 + 0.00215 = 0.0022
收錄日期: 2021-04-25 22:38:29
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20121112000051KK00069