开发者:上海品职教育科技有限公司 隐私政策详情

应用版本:4.2.11(IOS)｜3.2.5(安卓)APP下载

返回

Allez😃Sea · 2020年03月30日

问一道题：NO.PZ2018062016000091

  1. CFA I
  2. Quantitative

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

老师，为什么这题不可以用 x2-x1/b-a 来计算？

添加评论
1 个答案
已采纳答案

星星_品职助教 · 2020年03月30日

同学你好，

首先P(x1 ≤X ≤x2) = (x2 –x1)/(b – a)是Continuous Uniform Distribution才有的性质，这道题为 discrete random variable，本身就不能用。

其次这道题并不是在求P(23 ≤X ≤25) ，而是求Y takes 23 or 25，这是典型的A or B问题，所以需要求出Y=23和Y=25的概率，然后进行相加。

  • 1

    回答

  • 1

    关注

  • 395

    浏览
相关问题

NO.PZ2018062016000091 问题如下 Given a screte ranm variable Y, the set of all the possible Y value is Y = {20,21,22,23,24,25}.The estimatevalue of cumulative stribution function is in the table, whis the probability thY takes 23 or 25? A.0.50 B.0.45 C.0.75 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 thY takes 23 or 25 = p(23) + p(25) = 0.25+0.25 = 0.50 还是没看懂题，怎么看是求得是 1-p 而不是三个标准差呢

2022-12-01 14:11 1 · 回答

NO.PZ2018062016000091 问题如下 Given a screte ranm variable Y, the set of all the possible Y value is Y = {20,21,22,23,24,25}.The estimatevalue of cumulative stribution function is in the table, whis the probability thY takes 23 or 25? A.0.50 B.0.45 C.0.75 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 thY takes 23 or 25 = p(23) + p(25) = 0.25+0.25 = 0.50 有点没懂p23和p25怎么算的

2022-08-21 04:11 1 · 回答

NO.PZ2018062016000091 问题如下 Given a screte ranm variable Y, the set of all the possible Y value is Y = {20,21,22,23,24,25}.The estimatevalue of cumulative stribution function is in the table, whis the probability thY takes 23 or 25? A.0.50 B.0.45 C.0.75 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 thY 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

2022-07-07 09:41 1 · 回答

NO.PZ2018062016000091 请问，本题的问法是否错误，应该是P（23）anp(25)吧，而不是or

2022-01-27 17:01 1 · 回答

NO.PZ2018062016000091 0.45 0.75 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 thY takes 23 or 25 = p(23) + p(25) = 0.25+0.25 = 0.50老师，这个取到23或25的概率不可以用加法法则吗（两个至少取到一个的概率） 就是(0.25+0.25)-0.25*0.25

2021-08-04 00:03 1 · 回答