Hi,

is this list only related to R issues or it has a broader context regarding
questions and discussions about statistics. Is there any other email list or
forum for that? For example, I have a question regarding variance. It is
defined as:
variance = sum(sq(Xi-mean)) / (N-1)
and I never understood why not define it as
variance = sum(absolute(Xi-mean) / (N-1)

I read somewhere that this cannot be differentiated on 0. But, why is it
necessary to be able to differentiate it?

Thanks.

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