# Poisson Distribution - HP 49g+ User Manual

Graphing calculator.

probability of getting a success in any given repetition. The cumulative
distribution function for the binomial distribution is given by
F
(
n
,
p

## Poisson distribution

The probability mass function of the Poisson distribution is given by
f
(
λ
In this expression, if the random variable X represents the number of
occurrences of an event or observation per unit time, length, area, volume,
etc., then the parameter l represents the average number of occurrences per
unit time, length, area, volume, etc. The cumulative distribution function for
the Poisson distribution is given by
F
(
λ
Next, use function DEFINE („à) to define the following probability mass
functions (pmf) and cumulative distribution functions (cdf):
DEFINE(pmfb(n,p,x) = COMB(n,x)*p^x*(1-p)^(n-x))
DEFINE(cdfb(n,p,x) = Σ(k=0,x,pmfb(n,p,k)))
DEFINE(pmfp(λ,x) = EXP(-λ)*λ^x/x!)
DEFINE(cdfp(λ,x) = Σ(k=0,x,pmfp(λ,x)))
The function names stand for:
pmfb:
probability mass function for the binomial distribution
cdfb:
cumulative distribution function for the binomial distribution
pmfp:
probability mass function for the Poisson distribution
cdfp:
cumulative distribution function for the Poisson distribution
x
,
x
)
=
f
(
n
,
p
,
x
, )
k
=
0
λ
x
e
λ
,
x
)
,
x
x
!
x
,
x
)
f
(
λ
,
x
, )
x
k
=
0
x
=
0
1 ,
2 ,
,...,
n
0
1 ,
2 ,
,...,
.
0
1 ,
2 ,
,...,
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