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Array Calculation: Remove outliers

Posted on 2012-08-23
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Hello ,

I am not sure which is better way to handle outlier results out of array average calculations.  I have a bunch of fractions that get computed like this:
(A-B)/C
Now roughly 95% of the percentage results are ok and expected  but some results (red font) are bigger than expected for some weird data.
A            B      C      Results
93      93      95      0      74.55636
94      50000      96      -519.85417      74.55636
70000      96      97      720.659794      74.55636

What is a good way to get rid of these outliers and compute the average of the rest if the percentages?
One way is to get standard deviation for all the row fractions and giving a condition if :
Or each row - Keep on averaging the fraction if STD DEv is within the expected standard deviation value
How do I do this? Or any other real weighted percentage really…
EE-calculationwithoutOutliers.xlsx
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Question by:Rayne

LVL 24

Assisted Solution

If you have normal data then it is understood that +/- 2.6 standard deviations should cover outliers (special causes). Whether to do this by column would depend on the data.
EE-calculationwithoutOutliers.xlsx
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LVL 43

Accepted Solution

You could try a formula like

=AVERAGEIFS(E3:E145,E3:E145,"<>0",E3:E145,"<=1",E3:E145,">=-1")
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Author Closing Comment

Looks like we are getting somewhere, I will reward you for your efforts so far. I will post a follow up to get this further more close. But awesome help so far. <br />Thank you
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