Question

What is the probability that a "1 in a thousand" event happened sometime in the last year or 365 days?

Answer 1

Here, let X be the random variable indicating the number of times the event occurred.

X follows a binomial distribution with n = 365 and p = 1/1000 = 0.001

P(Event happened sometime in the last year) = 1 - P(Event never happened in the last year)

For a binomial variable,

So, we have

Probability that a "1 in a thousand" event happened sometime in the last year or 365 days = 0.3059