In: Statistics and Probability
Part 1: A particular telephone number is used to receive both voice calls and fax messages. Suppose that 20% of the incoming calls involve fax messages, and consider a sample of 20 incoming calls. (Round your answers to three decimal places.)
(a) What is the probability that at most 6 of the calls involve a fax message?
(b) What is the probability that exactly 6 of the calls involve a fax message?
(c) What is the probability that at least 6 of the calls involve a fax message?
(d) What is the probability that more than 6 of the calls
involve a fax message?
Part 2 : Suppose that 4% of the 2 million high school students who
take the SAT each year receive special accommodations because of
documented disabilities. Consider a random sample of 15 students
who have recently taken the test. (Round your probabilities to
three decimal places.)
(a) What is the probability that exactly 1 received a special
accommodation?
(b) What is the probability that at least 1 received a special
accommodation?
(c) What is the probability that at least 2 received a special
accommodation?
(d) What is the probability that the number among the 15 who
received a special accommodation is within 2 standard deviations of
the number you would expect to be accommodated?
(e) Suppose that a student who does not receive a special
accommodation is allowed 3 hours for the exam, whereas an
accommodated student is allowed 4.5 hours. What would you expect
the average time allowed the 15 selected students to be? (Round
your answer to two decimal places.)
Part 3: An airport limousine can accommodate up to four
passengers on any one trip. The company will accept a maximum of
six reservations for a trip, and a passenger must have a
reservation. From previous records, 45% of all those making
reservations do not appear for the trip. Answer the following
questions, assuming independence wherever appropriate. (Round your
answers to three decimal places.)
(a) If six reservations are made, what is the expected number of
available places when the limousine departs?
places
(b) Suppose the probability distribution of the number of
reservations made is given in the accompanying table.
Number of reservations | 3 | 4 | 5 | 6 |
Probability | 0.09 | 0.19 | 0.29 | 0.43 |
Let X denote the number of passengers on a randomly selected trip. Obtain the probability mass function of X.
x | 0 | 1 | 2 | 3 | 4 |
p(x) |