Lesson: Range and Standard Deviation

Comment on Range and Standard Deviation

I really like your videos.

I have a question - you say that it is necessary to square the numbers to account for the negative values?

If you were to just take the absolute value of all the values minus the mean, and then divide them by n, would that be the same as the standard deviation?

Nevermind, just watched the rest of the video! Thanks Brent :)

hi - maybe a silly error on my part? how'd you get SD of ~24.6 in the first set of numbers in your last example at the end of the video?

Average of 22. Take difference of each number (so absolute value of 1-22, 1-22, 3-22, and so on). Sum all those differences and divide by 10, the number of values in the set. I get ~20.6
gmat-admin's picture

You are using the informal definition to calculate the Standard Deviation of 20.6

I used the formal definition/formula to find that the Standard Deviation is approximately 24.6

On the GMAT, the informal definition is all you need (even though it yields a different SD)

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