Mathematics
OpenStudy (anonymous):

I have two questions about the attached problem

OpenStudy (anonymous):

OpenStudy (anonymous):

$E(XY)= \sum_{x,y}^{} xy f(x,y) = 29/18$ how does he calculated it and answered it 29/18 and the second question is that how does he calculated the values in red box (in table) ????????

OpenStudy (anonymous):

@TuringTest @experimentX @satellite73 any clue?

OpenStudy (anonymous):

lol here is a tedious numerical example!

OpenStudy (anonymous):

I am stuck at numerical calculation of this example I don't understand how does he calculated it

OpenStudy (anonymous):

you just have to grind it til you find it that is why it is tedious

OpenStudy (anonymous):

$\sum_{x,y}xyf(x,y)$ means sum over all possible pairs

OpenStudy (anonymous):

how?

OpenStudy (anonymous):

so we can begin to compute. for example if $$x=1,y=-1$$ you get $1\times (-1)\times \frac{1}{18}=-\frac{1}{18}$\]

OpenStudy (anonymous):

can we do it like $\sum_{x}^{?} xf(x) \sum_{y}^{?}yf(y)$ ?????

OpenStudy (anonymous):

nope

OpenStudy (anonymous):

ok, but in table it's 1/18 not -1/18

OpenStudy (anonymous):

you have to do what is says and you have $$3\times 3=9$$ products to consider

OpenStudy (anonymous):

ok lets go slow

OpenStudy (anonymous):

$f(1,-1)=\frac{1}{18}$ from the table right?

OpenStudy (anonymous):

how did you calculate it~?

OpenStudy (anonymous):

i didn't i looked in the table under the appropriate slot

OpenStudy (anonymous):

but it should be -1/18 why is it 1/18 in the table is it some printing mistake?

OpenStudy (anonymous):

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