NO.PZ2018062016000091
问题如下:
Given a discrete random variable Y, the set of all the possible Y value is Y = {20,21,22,23,24,25}.
The estimated value of cumulative distribution function is in the table, what is the probability that Y takes 23 or 25?
选项:
A.0.50
B.0.45
C.0.75
解释:
A is correct.
F(23) = P(Y≤ 23) = p(20) + p(21) + p(22) + p(23) = 0.55. F(22) = P(Y≤ 22) = p(20) + p(21) + p(22) = 0.30. So p(23) = 0.55-0.30 = 0.25.
For the same reason, F(25) = 1.00, F(24) = 0.75, p(25) = 1.00-0.75 = 0.25.
The probability that Y takes 23 or 25 = p(23) + p(25) = 0.25+0.25 = 0.50
本题中为什么P(23)和P(25)属于互斥事件 如何判断互斥事件的情况