Practice for Chapters 2, 3, 4
Chapter 2 Practice Questions
Also, Be able to do a Binomial (not on practice test, but on test) see HW solutions chapter 2-32, 2-33, 2-35
Also, Be familiar with Bayes’ Theorem (not on practice test) see HW solutions chapter 2-23 (can be done with Bayes’ Theorem) and 2-28 (using the complement)
Also, Be familiar with the exponential distribution (not on practice test) see HW solutions chapter 2-45
2.148
Fast Service Store has maintained daily sales records on the various size "Cool Drink" sales.
Assuming that past
performance is a good indicator of future sales, what is the probability of a customer purchasing a $0.50 "Cool Drink?"
“Cool Drink”
Price
Number
Sold
$0.25
75
$0.35
120
$0.50
125
$0.75
50
Total
400
ANSWER:
125/400 = 0.3125
2.151
A market research study is being conducted to determine if a product modification will be received well by the public.
A
total of 1,000 consumers are questioned regarding this product.
The table below provides information regarding this sample.
Positive
Reaction
Neutral
Reaction
Negative
Reaction
Male
240
60
100
Female
260
220
120
(a)
What is the probability that a randomly selected male would find this change favorable (positive)?
(b)
What is the probability that a randomly selected person would be a female who had a negative reaction?
(c)
If it is known that a person had a positive reaction to the study, what is the probability that the person is female?
ANSWER:
(a) 240/400 = 0.60
(b) 120/1000 = 0.120
(c) 260/500 = 0.520
2.152
In a production run of 200 units, there are exactly 10 defective items and 190 good items (200 total).
(a)
What is the probability that a randomly selected item is defective?
(b)
If two items are sampled without replacement, what is the probability that both are good?
(c)
If two items are randomly sampled without replacement, what is the probability that the first is good but the second
is defective?
ANSWER:
(a) 10/200 = 0.05
(b) (190/200)(189/199) = 0.902
(c) (190/200)(10/199) = 0.048
2.154
Last semester, the grade distribution in a quantitative methods course had the following distribution:
10 percent A, 25
percent B, 35 percent C, 10 percent D, and 15 percent W (withdrew).
(a)
If this grade distribution does not change this semester, what is the probability that a randomly selected student will
make at least a D?
(b)
If this grade distribution does not change this semester, what is the probability that a randomly selected student will
fail the course?
(c)
If this grade distribution does not change this semester, what is the probability that a randomly selected student who
finished the course (did not withdraw) made a grade of D or better?
ANSWER:
(a) 80 percent
(b) 5 percent
(c) 0.80/0.85 = 0.94
2.157
A southwestern tourist city has records indicating that the average daily temperature in the summer is 82 degrees F, which is
normally distributed with a standard deviation of 3 degrees F.
Based on these records, determine:
(a) the probability of a daily temperature between 79 degrees F and 85 degrees F