Formulas used
- Mean: x̄ = Σx ÷ n
- Sample variance: s² = Σ(x − x̄)² ÷ (n − 1)
- Population variance: σ² = Σ(x − x̄)² ÷ n
- Standard deviation: the square root of the variance
- Standard error: s ÷ √n
- Coefficient of variation: s ÷ |x̄| × 100%
Sample or population?
Use the sample figures when your data is a subset of a larger group and you want to estimate that group’s spread; this is the usual case. Use the population figures when your data includes every member of the group.
Quartiles
Q1, the median and Q3 split the sorted data into four equal parts. This calculator uses linear interpolation between data points, the same method as the QUARTILE.INC function in Excel and Google Sheets. The interquartile range (IQR = Q3 − Q1) measures the spread of the middle half of the data.
