canadiananalyst

Spanishesk Wrote:
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> Ok heres a question i ws thinking about when doing
> some work in excel...
>
> The variance of a 2 asset port = (Wa^2)(Var a) +
> (Wb^2)(Var b) + 2(Wa)(Wb)(Std a)(Std b)(Correl
> (a,b))
>
> My question is this...lets say the correlation is
> -1. Wouldnt it be possible to get a variance of
> the portfolio that is negative? What would that
> mean? or am i thinking a bout this wrong?

The variance of a 2 asset port = (Wa^2)(Var a) +(Wb^2)(Var b)
+2(Wa)(Wb)(Std a)(Std b)(Correl(a,b)) = (wa*Std a-wb*Std b)^2+2*Wa*Wb*Std a*Std b*(1+cor(a,b)). Each term is non-negative. Therefore, the sum is non-negative.