How to find standard deviation?

[rajivkumar]

Hi everyone, I’m trying to learn how to calculate standard deviation, but I keep getting confused with the formula.
Can someone explain the steps in a simple way (maybe with a small example)?
Also, what’s the difference between population and sample standard deviation?

 

[Oscar]

Find the mean, subtract it from each value, square the differences, calculate their average to get variance, then take the square root of the variance to obtain standard deviation.

 

[Peter]

To find standard deviation, first calculate the mean (average) of the numbers. Then subtract the mean from each value and square the result. Add all the squared values together and divide by the total number of values (for population) or by one less than the total (for sample). Finally, take the square root of that result. The answer is the standard deviation.

 

[alexmetro]

I tend to recall it as follows: determine the mean, subtract it of every number, square the differences, mean them, and next take a square root--it falls when you have only a few numbers to do it. The only actual difference is that population SD 1/n whereas sample SD 1/n-1 (a slight adaptation because you are using part of the data).