Standard deviation is one of those mathematical and statistical concepts that appear to be difficult but it is actually pretty easy. Standard deviation is simply an indication of the dispersion of numbers—that is how far the numbers are from the normal.
Here are the simplest steps on how to find the standard deviation:
1. Neatly write down the numbers that you need to work with.
2. Get the mean or average of the numbers.
- Add all the numbers you have.
- Divide by how many numbers there are.
3. Get the squared difference for each number.
- Subtract the mean from every number to get the difference.
- Square the difference (multiply the difference by itself).
4. Solve for the mean or average of all the squared differences. The answer you get is the variance.
5. Get the square root of the variance. The answer is the standard deviation.
Calculating using Microsoft Excel
- Open a new Excel spread sheet.
- Type in your data into individual cells.
- Select an empty cell, preferably one that is right next to the last digit that you entered. This is where the standard deviation will appear.
- On the empty cell type “ =STDEVP(
- Highlight the cells where your numbers are. Then press enter. This will enclose your data set into the formula. (Example =STDEVP(A1:Z99) )
- The standard deviation will appear on the selected cell.