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Originally Posted by Oblivionwarrior Ok. I found C to be 2/19. I integrated over the 2 regions. For the smaller region I got 3/2C, and for the larger region I got 8C. So 3/2C + 8C = 1, therefore C = 1/9.5 or 2/19.
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As has already been suggested, since the joint pdf is constant you can use simple geometry:
You require c(area of trapezium - area of triangle) = 1.
Area of trapezium = 5(1 + 6)/2 = 35/2.
Area of triangle = (4)(4)/2 = 8.
c(35/2 - 8) = 1 => c = 2/19 so yes you're correct.
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Originally Posted by Oblivionwarrior [snip]
To find the covariance would I use the formula E(XY) - E(X)E(Y)? To find E(XY) would I integrate again over the regions but this time have xy inside the integral? Would the C be 2/19 for both sides or would I need to split it up for both sides? |
Yes. Yes. Yes it would - c = 2/19 is the pdf so why on Earth would you split it up??