How do you figure standard deviation and variance when you have a group or list of numbers.

How do you figure standard deviation and variance when you have a group or list of numbers.
Do you need to show how you have done it by hand, or do you want an Excel solution?

The good news is, if you have to do it by hand, the Standard Deviation is simply the square root of the variance.


Let me know what kind of help you need.

Here is a good explanation: Learn Standard Deviation tutorial, definition, example, formula (http://www.easycalculation.com/statistics/learn-standard-deviation.php)

If you need the notation explained, just let me know. Some people need a process map instead of a formula.

In excel you can use function standard deviation and get answer in few seconds
Variance is square of std deviation

:eek:
How do you figure standard deviation and variance when you have a group or list of numbers.

This page might help with calculating standard deviation:

Standard Deviation Example (http://standard-deviation.appspot.com/)

Use excel formula
=STDEV( numbers)

Do you need to show how you have done it by hand, or do you want an Excel solution?

The good news is, if you have to do it by hand, the Standard Deviation is simply the square root of the variance.


Let me know what kind of help you need.

I would like both an excel solution and a process map, if you please!

Excel (if your numbers are in cell A1 to A20): =stdev(A1:A20)

"By hand":
1) Find the mean (I will call this X)
2) For every number (Xi), calculate (Xi - X)^2 (that is, the difference between the number and the mean, squared. I will call this Z^2)
3) Sum up all Z^2 (I will call this Sum(Z^2))
4) Divide Sum(Z^2) with the number of numbers minus one (that is, if you have 50 numbers, divide by 49).
5) Take the squareroot of the value you get in step 4.

This is for what is called experimental standard deviation.

Excel (if your numbers are in cell A1 to A20): =stdev(A1:A20)

"By hand":
1) Find the mean (I will call this X)
2) For every number (Xi), calculate (Xi - X)^2 (that is, the difference between the number and the mean, squared. I will call this Z^2)
3) Sum up all Z^2 (I will call this Sum(Z^2))
4) Divide Sum(Z^2) with the number of numbers minus one (that is, if you have 50 numbers, divide by 49).
5) Take the squareroot of the value you get in step 4.

This is for what is called experimental standard deviation.

Thank you very much, this should answer my problem :)

You can get clear idea from standard deviation (http://easycalculation.com/statistics/learn-standard-deviation.php) tutorials.