poisson
Probability
mass function 

Distribution 

Mean 

Variance 

The Poisson distribution is a discrete distribution bounded at 0 on the
low side and unbounded on the high side. The Poisson distribution is a
limiting form of the Hypergeometric distribution.
The Poisson distribution finds frequent use because it represents the
infrequent occurrence of events whose rate is constant. This includes
many types of events in time or space such as arrivals of telephone
calls, defects in semiconductor manufacturing, defects in all aspects
of quality control, molecular distributions, stellar distributions,
geographical distributions of plants, shot noise, etc. It is an
important starting point in queuing theory and reliability theory. Note
that the time between arrivals (defects) is Exponentially distributed,
which makes this distribution a particularly convenient starting point
even when the process is more complex. The Poisson distribution peaks
near lambda and falls off rapidly
on
either side.
Samples
 poisson(double
lambda)

Description
Generates a sample of the Poisson distribution.
Parameters
Name 
Type 
Description 
lambda 
double 
the rate
of
occurrence 
Result
Type 
Description 
int 
the
generated sample 
 poisson(double
lambda, java.util.Random
r)

Description
Generates a sample of the Poisson distribution using the
specified random number generator.
Parameters
Name 
Type 
Description 
lambda 
double 
the rate
of
occurrence 
r 
java.util.Random 
the
random
number generator 
Result
Type 
Description 
int 
the
generated sample 