When we find excess kurtosis, we need the exponent 4 of the deviations from the mean.
But we also need the standard deviation s (wich uses exponent 2 of the deviations from the mean).
Is there a quick way of going from Sum(Deviations)^4 --> the squared version (which can then be used in the stdev) ??
Like on page 386 of CFAI book 1, they do the ^4 long business, and then they just say what s is, so I'm wondering if there was a shortcut, because I seem to only be able to get s by restarting the whole squaring process... :S
But we also need the standard deviation s (wich uses exponent 2 of the deviations from the mean).
Is there a quick way of going from Sum(Deviations)^4 --> the squared version (which can then be used in the stdev) ??
Like on page 386 of CFAI book 1, they do the ^4 long business, and then they just say what s is, so I'm wondering if there was a shortcut, because I seem to only be able to get s by restarting the whole squaring process... :S