Description Computes the Poisson distribution, which is usually used to determine the probability of a certain number of repeated events taking place over time.
For example, you could use POISSON to calculate the probability that more than the average number of calls will pass through a telephone switching station over an hour's period.
Syntax POISSON (x, mean, cumulative)
| Argument | Description |
|---|---|
| x | A positive integer indicating the number of events you want to test the probability of happening over a given period. Decimal values will be rounded down to the nearest integer. Logical values are interpreted as 1 for TRUE and 0 for FALSE. |
| mean | A positive number indicating the average or expected number of events for the given test period. Logical values are interpreted as 1 for TRUE and 0 for FALSE. |
| cumulative | A logical value. True or 1 indicates you want to find the probability of at least x events happening. False or 0 indicates you want to find the probability of exactly x events happening. |
Equations when cumulative is FALSE:
when cumulative is TRUE: 
Examples This function returns .57, or a 57% probability:
See Also BETADIST, BINOMDIST, CHIDIST, COMBIN, CRITBINOM, FDIST, GAMMADIST, NORMDIST
