Find P(3) when µ = 4

there wasn't any prior information.

It was added

Explanation:

The Poisson PDF value is given by the function

P(x) = ( e^(-mu)*mu^x )/(x!)

where the exclamation mark indicates a factorial

In this case, mu = 4, so we can update the equation into

P(x) = ( e^(-4)*4^x )/(x!)

Now plug in x = 3 to finish off the problem

P(x) = ( e^(-4)*4^x )/(x!)

P(3) = ( e^(-4)*4^3 )/(3!)

P(3) = 0.1953668148129

P(3) = 0.20

Note: The 'e' is a special constant which is approximately e = 2.718, similar to how pi = 3.14 is a constant used often.