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- January 25th 2011, 03:30 AM #1

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## Mean value

how to determine E(y) for the joint probability density function fxy(x,y)=2/19 over the range 0<x<5 and 0<y and x-1<y<x+1?

I tried determining fy for 0<y<1 (fy1) and for 6>y>1 (fy2) separating the space where fxy is defined by the line y=1 and then

I integrated y*fy1dy from 0 to 6 and then y*fy2dy from 1 to 6 is that a correct method to do it? cause I have:

fy1=(y+1)*(2/19)

fy2=(4/19)

and the result I get is not correct? can anyone see where is my mistake?

- January 25th 2011, 04:49 AM #2

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- January 25th 2011, 05:47 AM #3

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It seems to me, and I may be mistaken, that you dont need the third integral. I mean, why didn't you go all the way from 1 to 5 in the second outer integral? And even if you wanted to split the integral why is the iner integral fom x-1 to 5? y is not limited at five I think! well plz clarify me, I would be thankfull

- January 25th 2011, 06:14 AM #4

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