Step-by-step explanation:
First we have to remember the Poisson distribution equation which is:
[tex]\frac{L^{r} }{r!} *e^{-r}[/tex]
Where L is defined by the mean in this case is 1.2
And r is the number of occurrences, in this case is 0,1,2,3 because we want to know the probability that at most 3 costumers arrive in one hour
Now we apply the formula with the given data and we will obtain
[tex]e^{-1.2}=0.30119[/tex]
[tex]{1.2^{} *e^{-1.2}=0.3614[/tex]
[tex]\frac{1.2^{2} }{2!} *e^{-1.2}=0.21686[/tex]
[tex]\frac{1.2^{3} }{3!} *e^{-1.2}=0.08674[/tex]
