Sample Probability Calculations

We can calculate probabilities for the Poisson( ) distribution using either the probability

distribution function (PDF) or the cumulative distribution function (CDF). We will denote

the PDF by f and the CDF by F . We will consider these functions for a variable X having

the Poisson(2) distribution.

> lambda:=2;

> f:=x->PoissonPDF(lambda,x);

> F:=x->PoissonCDF(lambda,x);

Below you will find three different ways to calculate P( ) .

> evalf(f(0)+f(1)+f(2)+f(3));

> evalf(sum(f(x),x=0..3));

> evalf(F(3));