# 3.5.3.1.4 Chi2cdf

## Description

Computes the lower/upper tail probability for the $\chi^2$ distribution with real degrees of freedom df.

## Syntax

double prob = chi2cdf(double x, double df[, int tail])

## Parameters

x

Input, the value of the Chi variate, must be nonnegative ($x>=0$).

df

Input, the degrees of freedom, $\nu$, of the distribution, $\chi^2$ must be positive($df>0$).

tail

Input, Optional. The tail probability type using for the $\chi^2$ distribution
• 1 = the for upper tail probability
• 2 = the lower tail probability (Default if not set)

prob

Output, the returned probability.

## Example

chi2cdf(150,3,1)=;     // ANS: 2.6349139284881E-32