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Q: Simple variance calculation ( Answered ,   0 Comments ) Question
 Subject: Simple variance calculation Category: Science > Math Asked by: charltonian-ga List Price: \$5.00 Posted: 30 Nov 2006 05:10 PST Expires: 30 Dec 2006 05:10 PST Question ID: 786962
 ```Ok, what I'm after is the formula for calculating the % variance between a current value and the previous value. I think this should be (where a is current, b is previous) ((a-b)/a)*100 I may be wrong about that - can someone confirm what it is AND provide a link to a reputable maths source showing that. Thanks``` Subject: Re: Simple variance calculation Answered By: palitoy-ga on 30 Nov 2006 06:06 PST Rated: ```Hello charltonian-ga, Thank-you for your question. I believe the formula you are looking for is usually called the percentage difference, rather than the percentage variance which may be why you have trouble locating your answer. The formula you have stated is the most common way in which you can calculate the percentage difference, the other is: ((a/b)*100%)-100 The two different formulae are discussed here: http://www.mathsisfun.com/percentage-difference.html Further evidence of the formulae can be found here: http://mathcentral.uregina.ca/QQ/database/QQ.09.01/tedd1.html http://mathforum.org/library/drmath/view/58083.html http://www.gcse.com/maths/percentage_difference.htm http://www.mdx.ac.uk/WWW/STUDY/glonumar.htm http://www.cliffsnotes.com/WileyCDA/Section/id-110141.html#math16 http://www.gomath.com/Questions/question.php?question=46424 I hope this fully answers your question. If you require any further assistance please ask for clarification and I will do my best to respond.```
 charltonian-ga rated this answer: and gave an additional tip of: \$1.00 `Excellent. Simple enough in the end but I needed it!`  