# Practice ```Practice
1. Explain the difference between a population and a sample.
2. What is a representative sample?
3. Define the following terms and give an example of each: a variable,
an observation, a data set.
4. Briefly describe the difference between a quantitative and a
qualitative variable. Explain the discrete and continuous variables.
Give one example of each of such variables.
5. What is the most appropriate level of measurement for Zip Codes?
6. Twenty persons were asked if they think they are financially better
off than their parents. The following are the responses of these 20
persons. (B indicates that a person is better off, W represents that
the person is worse off, and S stands for the same.)
B
W
W
S
B
B
S
B
B
B
B
W
B
W
S
B
W
S
S
B
a. Construct a frequency distribution table.
b. Calculate the relative frequencies and percentages for all
categories.
c. What percentage of these persons said that they are better off
than their parents?
d. What percentage of these persons said that they are either worse
off than their parents or the same?
e. Draw a histogram for the frequency distribution.
f. Draw a pie chart for the percentage distribution.
7. The following data give the amounts of electric bills (rounded to
the nearest dollar) for the past one month for 30 families.
75
38
55
34
41
42
47
63
35
26
55
39
56
61
45
29
73
71
48
61
24
42
76
47
33
46
67
67
51
52
a. Construct a frequency distribution table. Take 21 as the lower
limit of the first class and 10 as the width of each class.
b. Calculate the relative frequencies and percentages for all
classes.
c. What percentage of the families have a monthly electric bill of
\$61 or more?
d. What percentage of the families have a monthly electric bill of
\$40 or less?
e. Draw a histogram for the relative frequency distribution.
8. The following data give the number of cars rented on each of the
past 24 days at a car rental company.
12
31
9
8
22
17
18
19
29
25
32
23
33
37
31
25
28
33
15
18
25
26
30
23
Prepare a stem-and-leaf display. Arrange the leaves for each stem in
increasing order.
9. The following data give the amounts (in dollars) spent by 10
shoppers who shopped at a supermarket.
76
108
91
173
54
32
76
189
121
85
Find the mean and median. Do these data have a mode? If yes, what is
it?
10. The following data give the number of hours of overtime worked by
9 employees:
12
16
7
22
11
18
7
25
16
Find the range, variance, and standard deviation.
11. The following data give the time (in minutes) taken by 15 students
to complete a finance test.
45
29
53
38
29
46
33
51
39
47
47
51
56
38
32
a. Calculate the values of three quartiles.
12. The twenty aircraft owned by Central airlines have the following
ages: 7.0, 7.0, 7.0, 8.0, 8.0, 2.1, 2.7, 3.0, 3.2, 3.2, 15.0, 15.0,
15.0, 20.0, 20.0, 3.2, 5.0, 5.0, 5.0, and 5.0. Give the quantities
needed to construct a box-and-whisker plot.
```