The EXPON.DIST function returns the value of the probability density function or the cumulative distribution function for the exponential distribution.

  • This function was introduced in Excel 2010 and so is not available in earlier versions.
  • The EXPON.DIST function replaces the EXPONDIST function included in earlier versions of Excel.

Syntax

=EXPON.DIST(x,lambda,cumulative)

Arguments

Argument Description
x The value that the exponential distribution is to be evaluated at – must be positive
lambda The parameter of the distribution – must be > 0
cumulative A logical argument that specifies the type of distribution to be calculated:

  TRUE calculate the cumulative distribution function
  FALSE calculate the probability density function

Examples

  A B C D
1 Data Description    
2 0.2 Value of the function    
3 10 Argument value    
4        
5 Formula Result Notes
6 =EXPON.DIST(A2,A3,TRUE) 0.86466472 Cumulative exponential distribution function
7 =EXPON.DIST(A2,A3,FALSE) 1.35335283 Probability exponential distribution function

Usage note: Use EXPON.DIST to model the time between events, such as how long an automated bank teller takes to deliver cash. For example, you can use EXPON.DIST to determine the probability that the process takes at most 1 minute.

Common Function Error(s)

Problem What went wrong
#VALUE! Occurs if any of the supplied arguments are not non-numeric
#NUM! Occurs if either:

  the supplied value of x is negative
  the supplied lambda argument is ≤ 0
#NAME? Occurs when Analysis ToolPak add-in is not enabled

The exponential distribution is a continuous probability distribution, which is often used to model the time between events.

  • The equation for the probability density function is:    

    \[    f(x;\lambda) = \lambda^{-\lambda x}    \]

  • The equation for the cumulative distribution function is:

    \[    F(x;\lambda) = 1 - e^{-\lambda x}    \]

See Wikipedia for more information on exponential distribution.