Statistics 4.4 Combinations and Permutations

Important factorial expression to memorize is 0!

By special definition, the value of 0! is defined as 1.

Factorial

Factorials equal the products of strings of positive numbers. Factorial Is the product of all positive integers less than or equal to a given positive integer, n. Written n! Read "n factorial"

Special Permutation Rule

The special permutation rule states that anything permute itself is equivalent to itself factorial. Example: (3)3 =3!/(3 - 3)!=3!/0!= 3! = 3*2 *1 = 6

Permutation

is a selection of elements chosen from a group where the arrangement is specific. Notation: nPr Formula: n!/(n-r)!

Combination

is a selection of elements chosen from a group without regard to their order. notation: nCr Formula: n!/(n-r)! x r!

The difference between a combination and a permutation

is that order of the objects is not important for a combination.