Example 5.8 College Admissions (Binomial Probabilities Using Tables)
Early in August an undergraduate college discovers that is can accommodate a few extra students.
Enrolling those additional students would provide a substantial increase in revenue without increasing the
operating costs of the college; that is, no new classes would have to be added. From past experience the
college knows that 40% of those students admitted will actually enroll.
a. What is the probability that at most 6 students will enroll if the college offers admission to 10 more
students?
b. What is the probability that more than 12 will actually enroll if admission is offered to 20 students?
c. If 70% of those students admitted actually enroll, what is the probability that at least 12 out of 15
students will actually enroll?
Solution
Example 5.9 Sales of Airline Seats (Compute Binominal Probabilities using Minitab)
Have you ever agreed to give up your airplane ticket in return for a free ticket? Have you ever searched for
the cheapest flight so that you could visit a special friend? The following example provides some of the
analysis that leads to results such as overbooked flights and reduced fares on certain flights.
Suppose that you are in charge of marketing airline seats for a major carrier. Four days before the
flight date you have 16 seats remaining on the plane. You know from past experience data that 80% of the
people that purchase tickets in this time period will actually show up for the flight.
a. If you sell 20 extra tickets, what is the probability that you will overbook the flight or have at least
one empty seat?
b. If you sell 18 extra tickets, what is the probability that you will overbook the flight or have at least
one empty seat?
Solution
Example 6.5 Lightbulb Life (Normal Probabilities)
A company produces lightbulbs whose life follows a normal distribution, with mean 1,200 hours and
standard deviation 250 hours. If we choose a lightbulb at random, what is the probability that its lifetime
will be between 900 and 1,300 hours?
Solution
Example 6.8 Customer Sales (Normal Probabilities)
A saleswoman makes initial telephone contact with potential customers in an effort to assess whether a
follow-up visit to their homes is likely to be worthwhile. Her experience suggests that 40% of the initial
contacts lead to follow –up visits. If she contacts 100 people by telephone, what is the probability that
between 45 and 50 home visit will result?
Solution
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