Lee’s Lights sells lighting fixtures. Some customers are there only to browse, so Lee records the behaviour of all customers for a week to assess how likely it is that a customer will make a purchase. Lee finds that of 1000 customers entering the store during the week, 300 make purchases. Lee concludes that the probability of a customer making a purchase is 0.30.
QUESTION

If P (purchase) = 0.30, what is the probability that a customer doesn’t make a purchase?