# Documentation/Calc Functions/CHIDIST

CHIDIST

## Category:

Statistical Analysis

## Summary:

Returns the right-tailed probability value from the indicated chi-square that a hypothesis is confirmed.

The function calculates the area under the chi-square probability density function curve to the right of the specified chi-square value.

CHIDIST compares the chi-square value to be given for a random sample that is calculated from the sum of (observed value-expected value)^2/expected value for all values with the theoretical chi-square distribution and determines from this the probability of error for the hypothesis to be tested.

## Syntax:

CHIDIST(Number; DegreesFreedom)

## Returns:

Return a real number which is a right-tailed probability of the chi-square distribution. It is a probability hence it ranges from 0 to 1,i.e. [0,1].

## Arguments:

Number is a real number or a reference to the cell containing that number which is the chi-square value of the random sample used to determine the error probability.

DegreesFreedom is a positive integer or a reference to a cell containing that number which is the degrees of freedom of the experiment.

• If Number is less than or equal to 0, then, for valid values of DegreesFreedom, the function returns 1.
• If DegreesFreedom is less than 1, the function returns an error value.
• If DegreesFreedom is a non-integer numeric value, then the function uses its floor value, i.e. it is truncated to an integer.

The probability determined by CHIDIST can also be determined by CHITEST.

The formula for Chi distribution is:

where x>0 and returns 1 for x<=0. Here x is the Number and n is the DegreesFreedom.

For more details on Chi distribution, visit Wikipedia.

## Examples:

Formula Description Returns
=CHIDIST(13.27;5) If the Chi square value of the random sample is 13.27 and if the experiment has 5 degrees of freedom, then the hypothesis is assured with a probability of error of about 2%. 0.020975769403022
=CHIDIST(-13.27;5) The chi-square value of the random sample is negative so the function returns 1 by default for valid value of DegreesFreedom 1

CHIDIST