# Standard Deviation: 6 Steps to Calculation

The formula for **Standard Deviation **depends on whether you are analyzing *population *data, in which case it is called σ or estimating the population standard deviation from *sample *data, which is called s:

The steps to calculating the standard deviation are:

- Calculate the mean of the data set (x-bar or 1. μ)
- Subtract the mean from each value in the data set2.
- Square the differences found in step 23.
- Add up the squared differences found in step 34.
- Divide the total from step 4 by either N (for population data) or (n – 1) for sample data (Note: At this point 5. you have the
**variance**of the data)

Take the square root of the result from step 5 to get the standard deviation6.

**Example:**

**Step 1: **The average depth of this river, x-bar, is found to be 4’.

**Step 5: **The sample variance can now be calculated:

**Step 6: **To find the sample standard deviation, calculate the square root of the variance: