What this calculator does
Quartile deviation works out half the interquartile range: a robust spread measure, less sensitive to outliers than the SD. 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
FormulaQD = (Q3 − Q1) / 2; coefficient of QD = (Q3 − Q1) / (Q3 + Q1)
The inputs explained
| Field | What to enter |
|---|---|
| Data (comma or space separated) | A list of numbers, separated by commas or spaces. |