I.

MULTIPLE CHOICES
1. In a post office, the mailboxes are numbered from 1 to 4,500. These numbers represent
a. categorical data.
b. quantitative data.
c. either categorical or quantitative data.
d. since the numbers are sequential, the data is quantitative.

2. The scale of measurement used for variable data that is simply a label for the purpose of
identifying the attribute of an element is the _____ scale.
a. ratio
b. nominal
c. ordinal
d. interval

3. Height is an example of a variable that uses the _____ scale.

a. ratio
b. interval
c. nominal
d. ordinal

4. In a cumulative relative frequency distribution, the last class will have a cumulative relative
frequency equal to
a. one.
b. 100%.
c. the total number of elements in the data set.
d. the total of classes in the data set.

5. The numbers of hours worked (per week) by 400 statistics students are shown below.

Number of hours Frequency

0-9 20
10 - 19 80
20 - 29 200
30 - 39 100

The percentage of students who work at least 20 hours per week is

a. 25%.
b. 50%.
c. 75%.
d. 100%.

6. The heights (in inches) of 25 individuals were recorded and the following statistics were
calculated
mean = 70 range = 20
mode = 73 variance = 784
median = 74
The coefficient of variation equals
a. 11.2%.
b. 1120%.
c. 0.4%.
d. 40%.
7. Which of the following is not a measure of variability?
a. The range
b. The midrange
c. The standard deviation
d. The interquartile range

8. When n - 1 is used in the denominator to compute variance, the data set

a. is a sample.
b. is a population.
c. could be either a sample or a population.
d. is from a census.

9. The relative frequency of a class is computed by dividing the

a. midpoint of the class by the sample size.
b. frequency of the class by the midpoint.
c. sample size by the frequency of the class.
d. frequency of the class by the sample size.

10. A researcher has collected the following sample data.

15 12 16 18 15
16 17 15 12 14
The 75th percentile is
a. 13.
b. 14.
c. 15.
d. 16.

11. In the last month, Nancy purchased gasoline from four different gas stations. The following
table shows the price per gallon and the gallons of gasoline that she purchased.

Gallons Price per

Gas Station Purchased Gallon ($)
Texaco 20 3.95
Mobil 14 3.10
BP 18 3.80
Shell 12 3.99
Determine the weighted average price per gallon that Nancy paid for the gasoline.

a. 3.71
b. 3.73
c. 2.95
d. 4.00

12. The sample space refers to

a. any particular experimental outcome.
b. the sample size minus one.
c. the set of all possible experimental outcomes.
d. an event.
13. When the assumption of equally likely outcomes is used to assign probability values, the
method used to assign probabilities is referred to as the _____ method.
a. relative frequency
b. subjective
c. probability
d. classical

14. The addition law is potentially helpful when we are interested in computing the probability of
a. individual events
b. the intersection of two events
c. the union of two events
d. conditional events

15. The union of events A and B is the event containing all the sample points belonging to
a. B or A.
b. A or B.
c. A or B or both.
d. A or B, but not both.

16. The complement of event A is the event containing all the possible sample points:
a. Belonging to A
b. Not in event A
c. Can be in event A or not in event A
d. Not enough information.

17. If A and B are mutually exclusive events with P(A) = 0.3 and P(B) = 0.5, then P(A ∩ B) =
a. 0.30.
b. 0.15.
c. 0.00.
d. 0.20.

18. A method of assigning probabilities which assumes that the experimental outcomes are
equally likely is referred to as the _____ method.
a. objective
b. classical
c. subjective
d. experimental

19. If P(A) = 0.58, P(B) = 0.44, and P(A ∩ B) = 0.25, then P(A ∪ B) =
a. 1.02.
b. 0.77.
c. 0.11.
d. 0.39.

20. Which of the following is a required condition for a discrete probability function?
a. ∑f(x) = 0 for all values of
x
b. f(x) 1 for all values of x
c. f(x) < 0 for all values of x
 d. ∑f(x) = 1 for all values of
x

21. The following represents the probability distribution for the daily demand of computers at a
local store.

Demand Probability
0 0.15
1 0.25
2 0.35
3 0.2
4 0.05

The expected daily demand is

a. 1.0.
b. 1.75.
c. 2.0.
d. 1.09.

22. A uniform probability distribution is a continuous probability distribution where the

probability that the random variable assumes a value in any interval of equal length is
a. different for each interval.
b. the same for each interval.
c. at least one.
d. zero.

II. Short-answer questions

Question 1: A new soft drink is being market tested. It is estimated that 60% of consumers will like
the new drink. A sample of 96 taste tested the new drink.

a. Determine the standard error of the proportion

b. What is the probability that more than 70.4% of consumers will indicate they like the drink?
What is the probability that more than 30% of consumers will indicate they do not like the
c.
drink?
Question 2: Starting salaries of a sample of five management majors along with their genders are
shown below.
Salary
Employee (in $1,000s) Gender
1 30 F
2 28 M
3 22 F
4 26 F
5 19 M

a. What is the point estimate for the starting salaries of all management majors?
b. Determine the point estimate for the variance of the population.
c. Determine the point estimate for the proportion of male employees.
Question 3: Students of a large university spend an average of $5 a day on lunch. The standard
deviation of the expenditure is $3. A simple random sample of 36 students is taken.
a. What are the expected value and standard deviation?
b. What is the probability that the sample mean will be at least $4?
c. What is the probability that the sample mean will be at least $5.90?
Question 4: A local electronics firm wants to determine their average daily sales (in dollars.) A
sample of the sales for 64 days revealed an average sales of $160,000. Assume that the standard
deviation of the population is known to be $16,000.

a. Provide a 95% confidence interval estimate for the true average daily sales.
b. Provide a 98% confidence interval estimate for the true average daily sales.

Question 5: A random sample of 95 students at a local university showed that they work an average of
48 hours per month with a standard deviation of 12 hours. Compute a 95% confidence interval for the
mean of the population.
Question 6: The management of a grocery store has kept a record of bad checks received per day for a
period of 200 days. The data are shown below.

Number of Bad
Checks Received Number of Days
0 8
1 12
2 20
3 60
4 40
5 30
6 20
7 10

a. Develop a probability distribution for the above data.

b. Is the probability distribution that you found in Part “a” a proper probability distribution?
c. Determine the cumulative probability distribution f(x).
d. What is the probability that in a given day the store receives four or less bad checks?
e. What is the probability that in a given day the store receives more than 3 bad checks?