Can someone explain to me how(adsbygoogle = window.adsbygoogle || []).push({});

Cov(x,y)=[X-E(x))(Y-E(y)]

and this would equal 0 under the normal OLS assumption.

I know how to calculate the covariance, but X here is a matrix. So I don't understand the logic of this formula...

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# Having trouble understaning the notation co-variances

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