How to calculate standard deviation from mean

Deviation means how far from the normal

Standard Deviation

The Standard Deviation is a measure of how spread out numbers are.

You might like to read this simpler page on Standard Deviation first.

But here we explain the formulas.

The symbol for Standard Deviation is σ (the Greek letter sigma).

Say what? Please explain!

OK.

Let us explain it step by step.

Say we have a bunch of numbers like 9, 2, 5, 4, 12, 7, 8, 11.

To calculate the standard deviation of those numbers:

• 1.

  How to find mean

• Standard deviation symbol
• Standard deviation calculator
• Standard deviation examples with solutions
• How to find sample standard deviation

Work out the Mean (the simple average of the numbers)

• 2. Then for each number: subtract the Mean and square the result
• 3. Then work out the mean of those squared differences.
• 4. Take the square root of that and we are done!

The formula actually says all of that, and I will show you how.

The Formula Explained

First, let us have some example values to work on: