# Standard deviation?

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• Jun 19th 2010, 11:31 PM
lissakay
Standard deviation?
Pick a number between 0 and 7.

You now need to create a set of data that has at least 6 (no more than 10) values in it.

Your created values (data) need to have a standard deviation of 3.

You also need to explain how you came up with your values.

I am so so lost. Please show me how to do this.
• Jun 20th 2010, 02:34 AM
SpringFan25
The standard deviation is the Square root of the average square distance between the data and its mean.

The simplest way to do this would be to choose 6 data points, and give them all the same square distance from the mean. We want an average square distance of 3^2 =9, so I will make all my data have a distance of 3 from the mean.

You might find it easier to think along these lines instead
"If the standard deviation is 3 then the variance must be 9"
"The variance is the average squared deviation from the mean. I can get a variance of 9 by putting every point 3 units away from the mean"

Either way, The easiest way to to this is to choose a mean value (ill use 4). Then pick 3 points with a positive deviation of 3, and 3 points with a negative deviation of 3.

So i suggest
(4-3)
(4-3)
(4-3)
(4+3)
(4+3)
(4+3)

which is:
1,1,1,7,7,7

You can check that the mean of the above values is 4 and the standard deviation is 3
• Jun 20th 2010, 11:21 AM
lissakay
Thank you so much!
• Jun 28th 2010, 10:55 PM
CaptainBlack
Quote:

Originally Posted by lissakay
Thank you so much!

If you want to thank someone use the thanks button (it is the one with thumbs up icon, just below the post)

CB