Re: What is standard deviation?

From Stanford Wong's BJ21

Posted by CL on 8 Oct 1997, at 8:56 p.m., in response to Re: What is standard deviation?, posted by Bisser on 8 Oct 1997, at 4:33 p.m.

I like Bisser's simple explanation. Here are some more details. The numbers 1, 4, 7, 7, 11 have mean 6, but they deviate from the mean quite a lot. Namely, they deviate from the mean by 5, 2, 1, 1, and 5, respectively. The total deviation is 14. Consider another set of numbers 5, 6, 6, 6, 7 which also have a mean 6, they deviate from their mean by 1, 0, 0, 0, 1, respectively. The total deviation of this set of numbers is 2. So, the standard deviation of the first set of numbers is approximately 7 times as large as that of the second set. This argument is just an approximation (it is 100% correct if the data are normally distributed), but it gives you a good idea of what standard deviation is.

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