Standard Deviation Vs Variation
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 This topic has 3 replies, 4 voices, and was last updated 20 years, 10 months ago by Terry Krueger.

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November 14, 2001 at 4:15 pm #28222
Hi all
What I really want to know is the exact difference meaning between Standard Deviation and Variation. Standard deviation denotes the average distance from the mean, and variation denotes it’s square amount. What’s the main reason we control the variance rather than Standard deviation although Standard deviation give us easy to understand numeric answer because it tells how far from the mean.
And why for 6 sigma activity why we control the variance not standard deviation?0November 14, 2001 at 5:24 pm #69965The standard deviation is a measure of variation, usually applied to normal distributions, although it is also defined to be the square root of the second moment of any distribution.
The standard deviation is simply the square root of the variance. They are oneone. For some circumstances, such as linear combinations of normal variates, the variance is easier to work with (the variance of a sum is the sum of the variances). For other circumstances, such as a discussion about the “width” of the distribution, the standard deviation is easier to work with, since it is in the same units as the random variable itself.0November 15, 2001 at 3:50 am #69970
Dee UmbassParticipant@DeeUmbass Include @DeeUmbass in your post and this person will
be notified via email.I personally like working with variation better. I find it easier and a lot quicker to reduce a lot.Dee
0November 15, 2001 at 2:51 pm #69984
Terry KruegerMember@TerryKrueger Include @TerryKrueger in your post and this person will
be notified via email.Two things
Squaring a number eliminates negatives
Squaring also produces a nonlinear curve (like chisquare)
e.g.
2>4
4>16
16>256
and therefore visibility increases exponentially.0 
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