You can also conveniently calculate Poisson probabilities using Excel. The built-in POISSON function has the following characteristics:

POISSON(*x*, m, cumulative)

where:

cumulative = FALSE if you want the probability of exactly *x* occurrences

cumulative = TRUE if you want the probability of *x* or fewer occurrences

For instance, Figure 10.2 shows the POISSON function being used to calculate the probability that there will be exactly two accidents in the intersection next month.

Cell A1 contains the Excel formula =POISSON(2,1.8,FALSE) ...

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