What this calculator does
Range rule of thumb for standard deviation works out a quick estimate of standard deviation from just the minimum and maximum of a data set. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Minimum value | A number. Starts at 18. |
| Maximum value | A number. Starts at 82. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with minimum value
Every other input is held at the calculator’s starting values while minimum value varies. Select any row to load that scenario into the calculator.
| Minimum value | Estimated standard deviation | Range | Note |
|---|---|---|---|
| 9 | 18.250 | 73.000 | a rough approximation, most reliable for roughly normal data with n around 30 |
| 13.5 | 17.125 | 68.500 | a rough approximation, most reliable for roughly normal data with n around 30 |
| 18 | 16.000 | 64.000 | a rough approximation, most reliable for roughly normal data with n around 30 |
| 27 | 13.750 | 55.000 | a rough approximation, most reliable for roughly normal data with n around 30 |
| 36 | 11.500 | 46.000 | a rough approximation, most reliable for roughly normal data with n around 30 |
| 54 | 7.000 | 28.000 | a rough approximation, most reliable for roughly normal data with n around 30 |