Finding the value of a Poisson probability distribution (TI83+)

To find probability of a having ONLY a certain frequency (i.e. x = 3):
 * 1) Go to DISTR(2nd-VARS>DISTR>poissonpdf(
 * 2) Input 'poissonpdf(λ,x)', replacing the variables with their respective values

To find probability of having AT MOST a certain frequency (i. e. x < 3):
 * 1) Go to DISTR(2nd-VARS>DISTR>poissoncdf(
 * 2) Input 'poissoncdf(λ,x)', replacing the variables with their respective values