

Subject:
Need Solution to Weighted Average Problem ($20.00)
Category: Science > Math Asked by: vijaydga List Price: $20.00 
Posted:
02 Oct 2006 19:18 PDT
Expires: 01 Nov 2006 18:18 PST Question ID: 770318 
Need Solution to Weighted Average Problem ($20.00) The Problem: I have 3 scores s1, s2, s3 that are weighted at w1, w2, and w3 respectively to give an average score of s = (w1)(s1)+(w2)(s2)+(w3)(s3). Note: w1+w2+w3=1. s1, s2, s3 are all greater than 0 and between 0 and 100. Now, I lose the original scores s1, s2, and s3. All, I have is the average score s and the weights w1, w2, and w3. Given these four values, I want to find out what the average score would have been if I had weighted each score equally, i.e. w1=w2=w3=(1/3)  
 


There is no answer at this time. 

Subject:
Re: Need Solution to Weighted Average Problem ($20.00)
From: barnecaga on 03 Oct 2006 07:21 PDT 
sorry, can't be done. for proof, note that given the w1, w2, w3, and s in your clarification, both of the following sets of scores are possible: s1=87, s2=79, s3=93. mean=86.33 or s1=81, s2=81, s3=95. mean=85.67 there are, as livioflores says, an infinite number of possible scores. finite, but still more than a couple, if you know the original scores were integers. now, depending on why you want to know the mean, if you're interested in finding an upper and lower bound on the mean score, you might reask the question that way. assuming w1, w2, and w3 are all relatively close to each other, i suspect you could bound it within a reasonably tight range. cab 
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