Probability distribution doubts

[Homer Simpson]

1) If X and Y have joint probability distribution f(x,y) = 1/4 for x = -3 and y = -5, x = -1 and y = -1, x = 1 an y = 1, and x = 3 and y = 5, find cov(X,Y). i got 8. please confirm.

2) if joint pdf of X and Y is given by

f(x,y) = 1/3(x+y) for 0<x<1, 0<y<2
        =  0               elsewhere

find the variance of W = 3X+4Y-5

my answer is coming out weird. can someone show the working please?

[ani]

D fst one is cMing out to b 8 as x nd y hving xpctation =0
BUT in d scnd case is d f(x,y)=1/(3(x+y)) or just (x+y)/3???

[Homer Simpson]

its (x+y)/3

[ani]

Well..d 2. Nd one is cmin like 4. Something..

[Homer Simpson]

Whats 2 again? i didnt understand what you wrote in the reply?

[ani]

Well...its approximately 4... hve u got d same typ of answer??

On 5 Jun 2014 20:15, "tsuki [via Discussion forum]" <[hidden email]> wrote:

Whats 2 again? i didnt understand what you wrote in the reply?

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[Homer Simpson]

answer is 805/162 - not getting this. can you show the steps please??

[ani]

I m hvin some 703/162... may b some calculation mistake... I m just findin out d variances of x nd y.. and dn calculating it... upps..I forgot to minus d cov part... just do it.. I think we gonna hve d answer after subtracting it..

On 5 Jun 2014 20:19, "tsuki [via Discussion forum]" <[hidden email]> wrote:

answer is 805/162 - not getting this. can you show the steps please??

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[Homer Simpson]

ei covariance minus kyu hoga? X, Y have positive signs

[ani]

Ya ya.... it will b added... but I think I m havin calculation problems .as d cov is cumin lyk 12/81... but I m sure my steps are right

On 5 Jun 2014 20:28, "tsuki [via Discussion forum]" <[hidden email]> wrote:

ei covariance minus kyu hoga? X, Y have positive signs

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