EXPON.DIST Function

Basic Description

For a given value of x and parameter λ the Excel EXPON.DIST function calculates the value of the probability density function or the cumulative distribution function for the exponential distribution. The function is new in Excel 2010, so is not available in earlier versions of Excel. However, the Expon.Dist function is simply a renamed version of the Expondist function, that is available in earlier versions of Excel.

Syntax: EXPON.DIST( x, lambda, cumulative )

where the function arguments are:

x A positive number, denoting the value that the exponential distribution is to be evaluated at
lambda The parameter of the distribution (must be > 0)
cumulative A logical argument that specifies the type of distribution to be calculated. This can have the value TRUE or FALSE, meaning:

TRUE calculate the cumulative distribution function
FALSE calculate the probability density function
Plot of the Exponential Distribution Probability Density Function with the Parameter lambda set to 0.5, 1 and 2

Probability Density Exponential Distribution with λ = 0.5, 1 and 2

Expon.Dist Function Examples

Example 1 – Probability Density Function

The chart on the right shows the probability density functions for the exponential distribution with the parameter λ set to 0.5, 1, and 2. If you want to calculate value of the function with λ = 1, at the value x=0.5, this can be done using the Excel Expon.Dist function as follows :

=EXPONDIST( 0.5, 1, FALSE )

 

which gives the result 0.60653066.

Plot of the Cumulative Exponential Distribution with the Parameter lambda set to 0.5, 1 and 2

Cumulative Exponential Distribution with λ = 0.5, 1 and 2
Example 2 – Cumulative Distribution Function

The chart on the right shows the cumulative exponential distribution functions with the parameter λ equal to 0.5, 1 and 2.

If you want to calculate value of the function with λ = 1, at the value x=0.5, this can be done using the Excel Expon.Dist function as follows :

=EXPON.DIST( 0.5, 1, TRUE )

This gives the result 0.39346934.

 

Expon.Dist Function Errors

The following table lists the reasons for the most commonly encountered Excel errors, when using the Excel Expon.Dist function :

#NUM! Occurs if either the supplied value of x is negative or the supplied lambda argument is ≤ 0
#VALUE! Occurs if any of the supplied arguments are not non-numeric

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