In statistics, the exclamation mark (!) is used to denote the factorial of a non-negative integer. The factorial of a number n, represented as n!, is the product of all positive integers from 1 up to n. For example, if n is 5, then 5! = 5 × 4 × 3 × 2 × 1 = 120.
Factorials are especially useful in permutations and combinations, which are concepts in probability and statistics that deal with counting arrangements and selections. The factorial function helps in calculating the number of ways to arrange a set of objects or to select objects from a group, making it an essential tool in statistical analysis.