Σσς
MATHEMATICS
- Summation Σ (uppercase sigma).
- Structures: σ-algebra (sigma).
PROBABILITY
- Probability spaces: σ-algebra (F).
- σ(X) = σ-algebra generated by X.
STATISTICS
- Population standard deviation (σ).
- Variance (σ²) in normal models.
PRONUNCIATION
- Ancient Greek
- sound [s]
- Modern Greek
- σίγμα [ˈsiɣma] · sound [s]
IN FORMULAS
- Z = (X − μ) / σσ, the population standard deviation, is the unit of the z-score.See it explained at morrisonkuhlsen.com →
- Σ xᵢ = x₁ + x₂ + … + xₙThe uppercase Σ is the summation operator.
HOW TO WRITE IT — click to copy
lowercase
variant
uppercase
DON'T CONFUSE IT
- ∑ Σ Ε ∏ ∑ (U+2211, \sum) is the operator, larger and with more air; Σ (U+03A3) is the letter. Copied as text, they are different characters.
Note: notations vary between books/fields; these are the most common usages.