# variance and standard deviation

Discussion in 'DAT Discussions' started by issa, Aug 9, 2006.

1. ### issa Senior Member 5+ Year Member

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what are the formulas for variance and standard deviation? i found the formulas but they were confusing.

the question: 7 employees with a rating of 5,4,3,3,3,2,1
what is the standard deviation?

i remember that we have to find the avergae and then i don't remember the formula and to do next to solve this problem.

2. ### tinman831 ¯\_(ツ)_/¯ Staff MemberAdministrator DentistLifetime DonorVerified ExpertVerified Account 10+ Year Member

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Here's a link that explains it pretty well:

http://www.gcseguide.co.uk/standard_deviation.htm

1) find the average of the numbers.
2) subtract the mean from each number individually and square the result
3) add up all those squared results
4) divide the sum from step 3 by (n-1)
5) square root the result to get your standard deviation

3. ### DMD to Be not luffin' this weather. 5+ Year Member

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Hmm, and this is on the DAT? I haven't see it anywhere in review books...

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