Date: Oct 10, 2013 4:15 PM Author: Cristiano Subject: How to minimize a sum In this link:

http://en.wikipedia.org/wiki/Weighted_arithmetic_mean#Statistical_properties

there is the formula sigma(x_bar) = sqrt(...).

I need to find the n w's which give the smallest possible sigma(x_bar).

Please, could somebody help me?

Thank you

Cristiano