Revision sheet · Mathematics

Measures of dispersion

Mean deviation about the mean: $M . D . (x ˉ) = \frac{\sum ∣ x _{i} - x ˉ ∣}{n}$
Standard deviation: $σ = \frac{\sum ( x _{i} - x ˉ ) ^{2}}{n}$
Standard deviation, the shortcut form: $σ = \frac{\sum x _{i}^{2}}{n} - x ˉ^{2}$
Coefficient of variation: $C V = \frac{σ}{x ˉ} \times 100$