The standard deviation is a measurement of dispersion that can be interpreted as the average deviation or spread from the mean.
It is calculated using the formula where the mean .
The Standard Deviation can be found using these steps.
You can see the formulas if you wish.
Let's consider the name JAMES.
The variationis the result after step 4. The variation does not involve the sample size, so we don't know if it took five numbers or fifty numbers to achieve that variation.
The varianceis what we get when we divide the variation by the degrees of freedom. The variance doesn't have the same units as the original data, its units are squared.
The standard deviationis found by taking the square root of the variance. This returns us to the original units of the data and is the final measure of dispersion that we'll use.