In a busy coffee shop, which is a member of an international chain of coffee shops, 40% of customers order a pastry in addition to their drink. If 20 customers were selected at random during one business day, what is the probability that at least 11 of them did not order a pastry with their drink. Round your answer to 4 decimal places.
- 0.1275
- 0.3763
- 0.5956
- 0.7553
- None of the above
Answer
Correct answer: 0.7553.
Given that 40% of customers in a busy coffee shop, which is part of a multinational chain of coffee shops, order a pastry along with their beverage, it’s clear that pastries are widely appreciated.
Since each customer is independent and there are only two possibilities for each, the binomial distribution can be used to calculate x the number of customers who did not order a pastry with their cocktail.
X is binomial with n =20 and p = 1-0.4 = 0.60
q = 0.4
The probability that at least 11 of them did not order a pastry with their drink:
Note that binomial prob:
