05-30-2012, 09:27 AM
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#10 (permalink)
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Join Date: Jan 2012 Location: On a clear day, I can see Mt. Rainier ... but you can't count on the days to be clear here ...
Posts: 1,860
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Originally Posted by In_The_Wind How about some morning discreet math problems kids
Let X and Y be independent random variables. Prove that: V (X +
Y ) = V (X) + V (Y ).
V (X+Y ) = E[(X+Y )2]E[(X+Y )]2 = E[X2+2XY +Y 2](E[X]+
E[Y ])2 = E[X2] + E[2XY ] + E[Y 2] E[X]2 2E[X]E[Y ] E[Y ]2.
Answer
Hence we
have E[X2] E[X]2 + E[Y 2] E[Y ]2 = V (X) + V (Y ).
True story when i was taking discreet math I told my professor the very first day that I preferred to do my math out in the open and not discreetly he didnt think that was funny needless to say it was a longgggggggg semester | It'd be just like a discrete math professor to try to teach spelling right about then ... Sometimes, they get all confused about what they're supposed to be teaching like that. Posted via Mobile Device
Last edited by shy_guy; 05-30-2012 at 09:52 AM.
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