Line 22: Line 22:
 
----
 
----
 
==Question==
 
==Question==
'''Part 1. '''
+
1 (33 points)
  
Write Statement here
+
Let <math class="inline">\mathbf{X}</math>  and <math class="inline">\mathbf{Y}</math>  be two joinly distributed random variables having joint pdf
 +
 
 +
<math class="inline">f_{\mathbf{XY}}\left(x,y\right)=\left\{ \begin{array}{lll}
 +
1, &  & \text{ for }0\leq x\leq1\text{ and }0\leq y\leq1\\
 +
0, &  & \text{ elsewhere. }
 +
\end{array}\right.</math>
 +
 
 +
(a)
 +
 
 +
Are <math class="inline">\mathbf{X}</math>  and <math class="inline">\mathbf{Y}</math>  statistically independent? Justify your answer.
 +
 
 +
 
 +
(b)
 +
 
 +
Let <math class="inline">\mathbf{Z}</math>  be a new random variable defined as <math class="inline">\mathbf{Z}=\mathbf{X}+\mathbf{Y}</math> . Find the cdf of <math class="inline">\mathbf{Z}</math> .
 +
 
 +
(c)
 +
 
 +
Find the variance of <math class="inline">\mathbf{Z}</math> .
  
 
:'''Click [[ECE_PhD_QE_CNSIP_Jan_2006_Problem1.1|here]] to view student [[ECE_PhD_QE_CNSIP_Jan_2006_Problem1.1|answers and discussions]]'''
 
:'''Click [[ECE_PhD_QE_CNSIP_Jan_2006_Problem1.1|here]] to view student [[ECE_PhD_QE_CNSIP_Jan_2006_Problem1.1|answers and discussions]]'''

Revision as of 09:21, 10 March 2015


ECE Ph.D. Qualifying Exam

Communication, Networking, Signal and Image Processing (CS)

Question 1: Probability and Random Processes

January 2006



Question

1 (33 points)

Let $ \mathbf{X} $ and $ \mathbf{Y} $ be two joinly distributed random variables having joint pdf

$ f_{\mathbf{XY}}\left(x,y\right)=\left\{ \begin{array}{lll} 1, & & \text{ for }0\leq x\leq1\text{ and }0\leq y\leq1\\ 0, & & \text{ elsewhere. } \end{array}\right. $

(a)

Are $ \mathbf{X} $ and $ \mathbf{Y} $ statistically independent? Justify your answer.


(b)

Let $ \mathbf{Z} $ be a new random variable defined as $ \mathbf{Z}=\mathbf{X}+\mathbf{Y} $ . Find the cdf of $ \mathbf{Z} $ .

(c)

Find the variance of $ \mathbf{Z} $ .

Click here to view student answers and discussions

Part 2.

Write question here.

Click here to view student answers and discussions

Part 3.

Write question here.

Click here to view student answers and discussions

Part 4.

Write question here.

Click here to view student answers and discussions

Back to ECE Qualifying Exams (QE) page

Alumni Liaison

Meet a recent graduate heading to Sweden for a Postdoctorate.

Christine Berkesch