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#1 2011-02-28 02:34:08

onako
Member
Registered: 2010-03-28
Posts: 43

Ratio approximation

The following is an approximation problem. Given a ratio:

I wonder what steps to follow to give a reasonable approximation.
This is an intuition

.
Clearly, given that all b_i terms are the same, the approximation is the correct solution.
But, this is not the case. The question is, under which conditions (assumptions on a_i or b_i) is the
above approximation accurate.
I guess, the lower the standard deviation of the b_i's, the more accurate the approximation. But, suppose the
b_i's are [1,2,3,4,5,6,7...]. What condition needs be meet for the accurate approximation.
In a sense, the ratio I'm trying to approximate is the weighted average, and in the approximation I'm discarding
the weights. If this interpretation makes it easier to further interpret, please use it.

Also, as for the conditions, I thought of


How is this condition affecting the accuracy of the ratio approximation. Is the approximation more accurate with
this assumption.
Thanks

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#2 2011-02-28 21:41:34

onako
Member
Registered: 2010-03-28
Posts: 43

Re: Ratio approximation

The condition


definitely has influence, but I'm also interested how does the correlation between the a_i and b_i entries
affects the accuracy of the approximation.
Also, other observations might be of help.
Thanks

Last edited by onako (2011-02-28 21:42:26)

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