STAT201 Study Questions on Chapter 5
15th ed.
Q. 19) Suppose two events A and B are mutually exclusive. What is the probability of their joint
occurence?
When two events are mutually exclusive it means that if one occurs the other event cannot
occur. Therefore, the probability of their joint occurrence is zero
Q.49) The probability the cause and the cure for all cancers will be discovered before the year
2020 is 0.20. Which approach of probability does this illustrate?
Subjective.
Q.50) A chicken factort has several stores. When interviewing applications for server positions,
the owner would like to include information on the amount of tip a server can expect to earn per
checks (bill). A study of 500 recent checks indicated that the server earned the following
amounts in tips per 8-hour shift.
Amount of Tip
$0 up to $20
20 up to 50
50 up to 100
100 up to 200
200 and more
Total
Number
200
100
75
75
50
500
a) What is the probability of a tip of $200 or more?
b) Are the categories “$0 up to $20” , “$20 up to $50” and so on considered mutually
exclusive?
c) If the probabilities associated with each outcome were totaled, what would that total be?
d) What is the probability of a tip of up to $50?
e) What is the probability of a tip of less than $200?
a.
b.
c.
d.
e.
0.10, found by 50/500
Yes, mutually exclusive, because a given tip cannot fall in more than one category.
1.00
0.60, found by 300/500
0.90, found by 450/500 or 1 – (50/500)
Some other questions:
1) An automatic machine inserts mixed vegetables into a plastic bag. Past experience
revealed that some packages were underweight and some were overweight, but most of
them had satisfactory weight.
What is the probability of selecting three packages that are satisfactory?
Answer: P(all 3 satisfactory) = (0.9) (0.9) (0.9) = 0.729
2) A study of interior designers' opinions with respect to the most desirable primary color
for executive offices showed that:
What is the probability that a designer does not prefer blue?
Answer: Total is 400. So, P(prefer Blue) = 37/400 = 0.0925
P( not prefer Blue) = 1 – P (prefer Blue) = 1 – 0.0925 = 0.9075.
3) In a survey of employee satisfaction, the following table summarizes the results in
terms of employee satisfaction and gender.
a) What is the probability that an employee is Female and Dissatisfied? Answer: 0.22
b) What is the probability that an employee is Male or Dissatisfied?
Answer: P(M or D) = P(M) + P(D) – P(M&D) = 0.60 + 0.55 – 0.33
= 0.82
c) What is the probability that an employee is Satisfied given that the employee is Male?
Answer: Total male= 27 +33 = 60 out of 100.
P(S |M) = 27/60 = 0.45