Used to represent the population standard deviation, a measure of the dispersion or spread of a dataset

Represents the sum of f(i) for all integers i from a to b, inclusive. 'a' is the lower limit, 'b' is the upper limit, and 'i' is the index of summation

n(n+1)/2

n(n+1)(2n+1)/6

[n(n+1)/2]²

σ = √[Σ(xᵢ - μ)² / N], where xᵢ are individual data points, μ is the population mean, and N is the population size

Represented by 's' or 'SD', it estimates the population standard deviation using a sample of data. The formula differs slightly from the population standard deviation formula (denominator is N-1 instead of N)

Sigma notation can also represent infinite series, where the upper limit is infinity (∞). The series may converge to a finite sum or diverge

A series converges if its sum approaches a finite limit

A series diverges if it does not approach a finite limit

cΣᵢ₌ₐᵇ f(i) + dΣᵢ₌ₐᵇ g(i), where c and d are constants. Summation is linear