Microsoft Knowledge Base
Excel: POISSON() Function Returns #NUM! Error Value
Last reviewed: September 12, 1996
Article ID: Q104583
The information in this article applies to:
- Microsoft Excel for Windows, versions 4.0, 4.0a, 5.0
- Microsoft Excel for the Macintosh, versions 4.0, 5.0
SUMMARY
In Microsoft Excel, the POISSON() function will return a #NUM! error value if the mean argument (the second argument), raised to the power of the x argument (the first argument), exceeds 9.999E+307.
You will also receive a #NUM! error value if the x argument (the first argument) exceeds 170.
MORE INFORMATION
The POISSON() function returns the Poisson probability distribution. You can use this function to predict the number of events over a specific time, such as the number of cars arriving at a toll plaza in one minute.
Microsoft Excel computes the Poisson probability distribution with the following formula,
(e^-y) * (y^x) -------------- (x!)
where:
- e is the base of the natural logarithm, or 2.71828182845904
- y is the expected number of successes (the mean)
- x is the number of actual successes (x)
One of the components of the formula is y raised to the power of x (y^x). If this component exceeds 9.999E+307, the maximum possible positive number in Microsoft Excel, you will receive a #NUM! error value.
Another component of the formula computes the factorial of x (x!). If x exceeds 170, the factorial of x will exceed 9.999E+307, resulting in a #NUM! error.
In general, these errors only occur when you use numbers greater than 100 for the mean and x arguments.
REFERENCES
"Function Reference," version 4.0, pages 328-329
KBCategory: kbusage Last reviewed: September 12, 1996 |