In terms of Poisson and Binomial distributions, what is the complement of:
* At least half
* More than
1. Customers returning items to a store arrive at the customer service desk according to a Poisson process with arrival rate of 18 per 30 minute interval. The probability that an arriving person is extremely upset is 50%. What is the chance that more than 100 extremely upset customers arrived between 7 and 8 pm?
2. Now suppose that exactly 30 customers arrived in the first half hour of operations. What is the probability that at least half of them are extremely upset?
I know I have to rewrite these in terms of complements, but I'm not quite sure how.