首页 | 学习中心 | 注册 登录
返回列表 发帖
bmaggie

UID
137541 
帖子
3658 
主题
530 
注册时间
2009-7-1 
最后登录
2012-2-18 
1# 跳转到 » 倒序看帖
打印
tT
发表于 2010-4-12 15:20 | 只看该作者

Reading 8: Probability Concepts-LOS m习题精选

2010, interpret, function, border
Session 2: Quantitative Methods: Basic Concepts
Reading 8: Probability Concepts

LOS m: Calculate and interpret covariance given a joint probability function.

 

 

 

Given P(X = 20, Y = 0) = 0.4, and P(X = 30, Y = 50) = 0.6, then COV(XY) is:

A)
 120.00.
B)
 125.00.
C)
 25.00.

收藏 分享

bmaggie

UID
137541 
帖子
3658 
主题
530 
注册时间
2009-7-1 
最后登录
2012-2-18 
2#
发表于 2010-4-12 15:21 | 只看该作者

Given P(X = 20, Y = 0) = 0.4, and P(X = 30, Y = 50) = 0.6, then COV(XY) is:

A)
 120.00.
B)
 125.00.
C)
 25.00.


The expected values are: E(X) = (0.4 × 20) + (0.6 × 30) = 26, and E(Y) = (0.4 × 0) + (0.6 × 50) = 30. The covariance is COV(XY) = (0.4 × ((20 ? 26) × (0 ? 30))) + ((0.6 × (30 ? 26) × (50 ? 30))) = 120.

TOP

bmaggie

UID
137541 
帖子
3658 
主题
530 
注册时间
2009-7-1 
最后登录
2012-2-18 
3#
发表于 2010-4-12 15:22 | 只看该作者

Given P(X = 2, Y = 10) = 0.3, P(X = 6, Y = 2.5) = 0.4, and P(X = 10, Y = 0) = 0.3, then COV(XY) is:

A)
 -12.0.
B)
 24.0.
C)
 6.0.

TOP

bmaggie

UID
137541 
帖子
3658 
主题
530 
注册时间
2009-7-1 
最后登录
2012-2-18 
4#
发表于 2010-4-12 15:22 | 只看该作者

Given P(X = 2, Y = 10) = 0.3, P(X = 6, Y = 2.5) = 0.4, and P(X = 10, Y = 0) = 0.3, then COV(XY) is:

A)
 -12.0.
B)
 24.0.
C)
 6.0.


The expected values are: E(X) = (0.3 × 2) + (0.4 × 6) + (0.3 × 10) = 6 and E(Y) = (0.3 × 10.0) + (0.4 × 2.5) + (0.3 × 0.0) = 4. The covariance is COV(XY) = ((0.3 × ((2 ? 6) × (10 ? 4))) + ((0.4 × ((6 ? 6) × (2.5 ? 4))) + (0.3 × ((10 ? 6) × (0 ? 4))) = ?12.

TOP

zaestau

Rank: 2

UID
72515 
帖子
873 
主题
0 
注册时间
2007-9-24 
最后登录
2020-5-12 
5#
发表于 2010-4-26 23:34 | 只看该作者
c

TOP

返回列表