Texas Instruments TI-83 PLUS - Manual (Page 435)

TI-83 Plus Inferential Statistics and Distributions 432
poissonpdf(
poissonpdf( computes a probability at x for the discrete Poisson
distribution with the specified mean m , which must be a real number > 0.
x can be an integer or a list of integers. The probability density function
(pdf) is:

, 2 , 1 , 0 , ! / ) (
= = −
x x e x f x
µ µ
poissonpdf(
m
, x )
poissoncdf(
poissoncdf( computes a cumulative probability at x for the discrete
Poisson distribution with the specified mean m , which must be a real
number > 0. x can be a real number or a list of real numbers.
poissoncdf( m , x )