# Factorial function

To use this function, choose Calc > Calculator.

The factorial of a nonnegative integer, n, is the product of all the consecutive integers from 1 to n, inclusive. The notation ! is used to represent the factorial. For example, 5! = 1* 2 * 3 * 4 * 5 = 120. By definition, 0! = 1.

## Syntax

FACTORIAL(number of items)

The value of number of items must be greater than or equal to 0. You can enter a column or constant. Missing values are not allowed.

## Example

Calculator expression Result
FACTORIAL(6) 720

## Uses

Use factorials to calculate:
• Probabilities, such as the chance of observing a certain number of successes in a binomial experiment (where each trial results in one of two outcomes). For example, if a drug is effective for 90% of patients, the probability that all five patients in a sample who take the drug will respond to the drug is 5!/(5!0!) (0.9)5(0.1)0 = 0.590 or 59%.
• Permutations, the number of possible ways to order the elements in a set. For example, there are 3! or 6 ways to order a set of 3 items. Permutations are important in computer security and data encryption.
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