واباژش ِ پوآسون vâbâžeš-e Poisson
*Fr.: distribution de Poisson*
A → *probability function* that characterizes
→ *discrete*
→ *random* events occurring independently of one another within
some definite time or space. It may be regarded as an approximation of the
→ *binomial distribution*
when the number of events becomes large and the probability of success
becomes small. The Poisson distribution is expressed by:
*f*(*x*) = (λ^{x}*e*^{-λ})/*x*!,
where λ is the mean number of successes in the interval,
*e* is the base of the → *natural logarithm*, and
*x* is the number of successes we are interested in. Named after Siméon Denis Poisson (1781-1840), French mathematician, who developed
the application of
Fourier series to physical problems and made major contributions to the theory of
probability and to the calculus of variations; → *distribution*. |