Re: Why is arithmetic mean being used in calculating standard deviation!? Why not some thing else!?


"m7ossny" <m7ossny@xxxxxxxxx> wrote in message
news:1166169472.959637.121260@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Google for "median absolute deviation"I have got a postgraduate degree in
statistics and until you mentioned it I
had never heard of it.

Like standard deviation, this is a measure of dispersal.

According to
http://www.itl.nist.gov/div898/handbook/eda/section3/eda356.htm

MAD= median (mod(Y(i) - median of Y))

Unfortunately it is virtually impossible to do any maths on a mod(ulus).

Whereas a square such as (Y(i) - Mean)^2 or possibly involving the median
also has only a positive value but can manipulated algebraically and have
differentiation and integration carried out on it.

Nick

So what you are saying is that it is meaningless, or it has some
advantages too.

Exactly what I said. Not that it was meaningless - but doing calculations
and maths on moduli is difficult whereas squares and square roots are much
easier for making general propositions about.

The normal measure of dispersal is the standard deviation. Other measures
used to describe a distribution are the skewness and kurtosis.

Nick


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