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September 13th, 2007, 05:17 PM   #1
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Forecasts for groups of items tend to be more accurate...


Does anyone have an idea how to mathematically prove that

"Forecasts for groups of items tend to be more accurate than forecasts for individual items because forecasting errors among items in a group usually have a cancelling effect."


Appreciate any response,
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September 14th, 2007, 06:42 AM   #2
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Most of the work would be in stating the problem mathematically. For example, if the statement was:

"Suppose x_1, x_2, ..., x_n are real numbers. Then |(x_1 + x_2 + ... + x_n)|/n >= (|x_1| + |x_2| + ... + |x_n|)/n."

This shows that in the worst case the average total error is the same as the average individual error.
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