User:Mmatth/sandbox

Hi all, this is an observation for https://en.wikipedia.org/wiki/Covariance I think there is an error calculating de standard deviation for the first example, before calculating the value for the covariance between X and Y: For the X variable, which is taking values in {1,2}, N=2 and mean equal 3/2, I am getting, in fact, 1/2. However, for the variable Y taking values in {1,2,3}, applying the formula with N=3 and mean equal 2, the value I get for the standard deviation is the square root of 2/3, not the square root of 1/2, as it says in the article. Can anyone tell me where I am wrong?