answer to 3.9.5
John Hop-Doan Nguyen (154adjhn@pic.ucla.edu)
Wed, 08 Nov 95 08:57:20 -0800
I'm not sure I understand Myron's answer to Karen's question, so I hope I'm not
repeating the same answer. I answered E(X2) by following Example 3.8.4. Since
you're taking the summation to infinity, the expected value will look like:
(e^-4 4^x-1)4/(x-1)! . Since the factor of 4 can go outside the summation,
all you have to do is set m=x-1 and you'll get:
4 * summation of (e^-4 4^m)/m! . The value of the sum is 1 since you're taking
the summation of a pdf at all it's values. Hope that explained it...
I also have a question about last week's homework. I tried to do question
3.8.9 (a) by solving for a geometric summation (c/2)^k. When I do that, I only
get 2/(2-c) as my answer. But the back of the book says its c/(2-c). Where
did I go wrong?
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