
#1
Apr112, 11:41 PM

P: 4

Hi guys,
I'm really stuck on the following questions, not sure as to how to approach it: Let X and Y be random variables for which the joint pdf is as follows: f(x,y) = 2(x+y) for 0 <= x <= y <= 1 and 0 otherwise. Find the pdf of Z = X + Y And also: Suppose that X is a random variable for which the mgf is as follows: /u(t) = e^(t^2 + 3t) for minus infinity < t < infinity Find the mean and variance for X. I know that the answers are 3 and 2 respectively, but was unsure how they got to the answer, do I need to integrate by parts? Any help would be appreciated! Thanks guys :) 



#2
Apr212, 04:01 PM

Sci Advisor
P: 5,939





#3
Apr312, 12:11 AM

P: 4

Figured out second question now, pretty straightforward in hindsight. Any help on the first one? ;)




#4
Apr312, 12:16 AM

P: 4,570

Joint pdf question and mgf 


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