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4. (a) For the random variable X, show that E[(x - a)?] is minimized when a = E(X). (b) For random variables X and Y, show th

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Random Vartable E (x-a= E(X-EN+ E)-a) =E(x-E)+E-at +2EE E (EO) E 0 -a3 EX- EW)as [EO)-a]0. E (X-a i8 minimen, whan a EC ClearTo pove: EC) E)EY) NOte that, E(dxipy)0,ER, PER ECK) +ECY+ ECY) (ax-py)0, kpeR Avso NOW, let E(Y& p- E(x) 1 2oAp Elxy) 2af E(

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