This is a Poisson distribution. The formula for calculating Poisson distribution is given as :
P (X = x) =
λ = 3.5
To find the probability that at most one accident occur today implies that , accident might not happen at all , the maximum accident that can happen is 1, substituting this into the formula , we have
P(X=0) =
P(X=0) = 0.0302
P(X=1) =
P(X=1) = 0.1057
Therefore , the probability that at most one accident occurs today.