Poisson and Exponential Distributions

A set of vocabulary flashcards reviewing key concepts, parameters, examples, and Excel functions for the Poisson and exponential distributions.

Shape of the Poisson Distribution

The characteristic curve shared by all Poisson distributions, where the probabilities first increase and then decrease.

Parameter $\lambda$ (Bank Arrival Example)

The value representing the expected number of customer arrivals per hour in a Poisson-distributed arrival pattern.

Parameter $\lambda$ (Retail Orders Example)

The value representing the expected number of customer orders for a particular product in a week in a Poisson distribution.

Interarrival Times

The times between customer arrivals, most commonly modeled using the continuous exponential distribution.

Exponential Distribution

A continuous probability distribution with parameter $\lambda > 0$ used primarily to model interarrival times, whose density function is defined for $x > 0$.

Mean and Standard Deviation of the Exponential Distribution

Measures of center and spread that are both equal to the reciprocal of the parameter $\lambda$ ($\frac{1}{\lambda}$).

EXPONDIST

The Excel function used to calculate the probability to the left of a given value $x > 0$ for any exponential distribution.

EXPON.DIST

The updated Excel function introduced in Excel 2010 that replaced EXPONDIST to calculate exponential distribution probabilities.