# Documentation/Calc Functions/CHIDIST

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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.

## Additional details:

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