Practica 1
Practica 1
Practica 1
True/False
2. The arithmetic mean is the sum of the observations divided by the total number
of observations.
3. For a set of data arranged or sorted in numerical order, the value of the
observation in the center is called the weighted mean.
5. If a variable is measured at the interval level, all the values are included when
computing the mean.
6. A variable measured at the interval level can have more than one arithmetic
mean.
7. The mode is the value of the observation that appears most frequently.
8. A distribution that has the same shape on either side of the center is said to be
symmetrical.
9. A negatively skewed distribution is not symmetrical. The long tail is to the left
or in the negative direction.
13. The median can be determined for any set of interval-level data.
14. Extremely high or low scores affect the value of the median.
16. For salaries of $102,000, $98,000, $45,000, $106,000 and $101,000, the
arithmetic mean would be an appropriate average.
17. Three persons earn $8 an hour, six earn $9 an hour, and one earns $12 an hour.
The weighted mean hourly wage is $9.
18. For any distribution, there are an equal number of values above the mean and
below it.
19. For a data set with an even number of ungrouped values, the median is the
arithmetic mean of the two middle values.
20. For a data set with an even number of ungrouped values, half of the values will
be less than the median.
21. In a negatively skewed distribution, the mean is always greater than the
median.
22. In a negatively skewed distribution, the mean is smaller than the median or
mode and the mode occurs at the peak of the curve.
23. In a positively skewed distribution, the mode is greater than the median.
25. The mean deviation is the mean of the actual values of the deviations from the
arithmetic mean.
26. The variance is the mean of the sum of the squared deviations between each
observation and the median.
27. The standard deviation is the positive square root of the variance.
29. The Empirical states that about 68% of the observation will lie within one
standard deviation of the mean; about 95% of the observations will lie within two
standard deviations of the mean; and virtually all (99.7%) will lie within three
standard deviations of the mean.
31. For a symmetrical distribution, the variance is equal to the standard deviation.
32. In a company, the standard deviation of the ages of female employees is six
years and the standard deviation of the ages of male employees is ten years. These
statistics indicate that there is more spread in the ages of the female employees.
33. If we find the deviation of each value from the median, the sum of these
deviations is always zero.
35. The range cannot be computed for data grouped in a frequency distribution
having an open end.
Multiple Choice
36. For which measure of central location will the sum of the deviations of each
value from the data's average will always be zero?
A) Mode
B) Mean
C) Median
D) Geometric mean
E) None of the above
37. For a set of grouped or ungrouped data, which measures of central location
always have only one value?
A) Mode and median
B) Mode and mean
C) Mode and geometric mean
D) Mean and median
38. Which measures of central location are not affected by extremely small or
extremely large values?
A) Mean and median
B) Mean and mode
C) Mode and median
D) Geometric mean and mean
E) None of the above
40. For a data set, half of the observations are always greater than the ________ .
A) Median
B) Mode
C) Mean
D) Geometric mean
41. What is the lowest level of measurement that a median can be computed?
A) Nominal
B) Ordinal
C) Interval
D) Ratio
42. For an ungrouped data set with an odd number of observations that have been
sorted or arrayed from smallest to largest values, where is the median located?
A) n
B) n/2
C) (n + 1)/2
D) n + 1/2
47. In the calculation of the arithmetic mean for grouped data, which value is used
to represent all the values in a particular class?
A) The upper limit of the class
B) The lower limit of the class
C) The frequency of the class
D) The cumulative frequency preceding the class
E) The class midpoint.
48. On a survey questionnaire, students were asked to indicate their class rank in
college. If there were only four choices from which to choose, which measure(s)
of central location would be appropriate to use for the data generated by that
questionnaire item?
A) Mean and median
B) Mean and mode
C) Mode and median
D) Mode only
E) Median only
49. What is the median of 26, 30, 24, 32, 32, 31, 27 and 29?
A) 32
B) 29
C) 30
D) 29.5
51. A sample of light trucks using diesel fuel revealed the following distribution
based on fuel efficiency, i.e., miles per gallon (mpg).
mpg Number of Trucks
10 up to 13 2
13 up to 16 5
16 up to 19 10
19 up to 22 8
22 up to 25 3
25 up to 28 2
52. The ages of newly hired, unskilled employees were grouped into the following
distribution:
Ages Number
18 up to 21 4
21 up to 24 8
24 up to 27 11
27 up to 30 20
30 up to 33 7
A) 106.4
B) 101.4
C) 111.4
D) 105.0
E) 20.0
54. The net annual sales of a sample of small retail clothing stores were organized
into the following relative frequency distribution.
Net Sales (in $ millions) Percent of Total
1 up to 4 13
4 up to 7 14
7 up to 10 40
10 up to 13 23
13 or more 10
56. During the past six months, the purchasing agent bought:
Tons of Coal 1,200 3,000 500
Price per Ton $28.50 $87.25 $88.00
57. A sample of single persons receiving social security payments revealed these
monthly benefits: $826, $699, $1,087, $880, $839 and $965. How many
observations are below the median?
A) 0
B) 1
C) 2
D) 3
E) 3.5
58. The number of work stoppages in a highly industrialized region for selected
months are: 6, 0, 10, 14, 8 and 0. What is the median number of stoppages?
A) 0
B) 6
C) 7
D) 8
E) 3
59. The U.S. Federal Aviation Administration reported that passenger revenues on
international flights increased from $528 million in 1983 to $5,100 million in
2006. What is the geometric mean annual percent increase in international
passenger revenues?
60. The Investment Company Institute reported in its Mutual Fund Fact Book that
the number of mutual funds increased from 5725 in 1995 to 7977 in 2005. What is
the geometric mean annual percent increase in the number of funds?
A) 1.034
B) 3.37
C) 39.34
D) 71.77
E) 633.5
61. Assume a student received the following grades for the semester: History, B;
Statistics, A; Spanish, C; and English, C. History and English are 5 credit hour
courses, Statistics a 4 credit hour course and Spanish a 3 credit hour course. If 4
grade points are assigned for an A, 3 for a B and 2 for a C, what is the weighted
mean for the semester grades?
A) 4.00
B) 1.96
C) 2.61
D) 3.01
E) 2.88
62. Production of passenger cars in Japan increased from 3.94 million in 1994 to
6.74 million in 2004. What is the geometric mean annual percent increase?
A) 4.0
B) 1.9
C) 5.5
D) 16.6
E) 47.3
63. A sample of the paramedical fees charged by clinics revealed these amounts:
$55, $49, $50, $45, $52 and $55. What is the median charge?
A) $47.50
B) $51.00
C) $52.00
D) $55.00
65. A bottling company offers three kinds of delivery service – instant, same day
and within five days. The profit per delivery varies according to the kind of
delivery. The profit for an instant delivery is less than the other kinds because the
driver has to go directly to a grocery store with a small load and return to the
bottling plant. To find out what effect each type of delivery has on the profit
picture, the company summarized the data in the following table based on
deliveries for the previous quarter.
Number of Deliveries
Type of Delivery During the Quarter Profit per Delivery
Instant 100 $ 70
Same day 60 100
Within five days 40 160
66. The U.S. Department of Education reported that for the past seven years 4,033,
5,652, 6,407, 7,201, 8,719, 11,154, and 15,121 people received bachelor's degrees
in computer and information sciences. What is the annual arithmetic mean number
of degrees awarded?
A) About 12,240
B) About 8,327
C) About 6,217
D) About 15,962
67. Which measure of central location is found by arranging the data from
smallest to largest and selecting the middle value?
68. The number of students at a local university increased from 2,500 students to
5000 students in 10 years. Based on a geometric mean, the university grew at an
average percentage rate of
A) 2,500 students per year
B) 1.071 percent per year
C) 7.1 percent per year
D) 250 students per year
69. A question in a market survey asks for a respondent's favorite car color.
Which measure of central location should be used to summarize this question?
A) Mode
B) Median
C) Mean
D) Geometric mean
70. Sometimes, data has two values that have the highest and equal frequencies.
In this case, the distribution of the data can best be summarized as
A) symmetric
B) bimodal (having two modes)
C) positively skewed
D) negatively skewed
76. A purchasing agent for a trucking company is shopping for replacement tires
for their trucks from two suppliers. The suppliers' prices are the same. However,
Supplier A's tires have an average life of 60,000 miles with a standard deviation of
10,000 miles. Supplier B's tires have an average life of 60,000 miles with a
standard deviation of 2,000 miles.
Which of the following statements is true?
A) The two distributions of tire life are the same
B) On average, Supplier A's tires have a longer life then Supplier B's tires
C) The life of Supplier B's tire is more predictable than the life of Supplier A's
tires
D) The dispersion of Supplier A's tire life is less than the dispersion of Supplier
B's tire life
77. The sum of the differences between sample observations and the sample mean
is
A) Zero
B) The mean deviation
C) The range
D) The standard deviation
79. Which of the following measures of dispersion are based on deviations from
the mean?
A) Variance
B) Standard deviation
C) Mean deviation
D) All of the above
80. What is the relationship between the variance and the standard deviation?
A) Variance is the square root of the standard deviation
B) Variance is the square of the standard deviation
C) Variance is twice the standard deviation
D) No constant relationship between the variance and the standard deviation
82. What is the range for a sample of March electric bills amounts for all-electric
homes of similar sizes (to the nearest dollar): $212, $191, $176, $129, $106, $92,
$108, $109, $103, $121, $175 and $194.
A) $100
B) $130
C) $120
D) $112
84. Which measure of dispersion disregards the algebraic signs (plus and minus)
of each difference between X and the mean?
A) Standard deviation
B) Mean deviation
C) Arithmetic mean
D) Variance
85. The following are the weekly amounts of welfare payments made by the
federal government to a sample of six families: $139, $136, $130, $136, $147 and
$136. What is the range?
A) $0
B) $14
C) $52
D) $17
87. The ages of a sample of the typewriters used by the typists in the typing pool
were organized into the following table:
88. The weights of a sample of crates ready for shipment to Laos are (in
kilograms): 103, 97, 101, 106 and 103. What is the mean deviation?
A) 0 kg
B) 6.9 kg
C) 102.0 kg
D) 2.4 kg
E) 9.0 kg
89. The closing prices of a common stock have been 61.5, 62, 61.25, 60.875 and
61.5 for the past week. What is the range?
A) $1.250
B) $1.750
C) $1.125
D) $1.875
90. Ten experts rated a newly developed chocolate chip cookie on a scale of 1 to
50. Their ratings were: 34, 35, 41, 28, 26, 29, 32, 36, 38 and 40. What is the mean
deviation?
A) 8.00
B) 4.12
C) 12.67
D) 0.75
91. The weights (in kilograms) of a group of crates being shipped to Panama are
95, 103, 110, 104, 105, 112 and 92. What is the mean deviation?
A) 5.43 kg
B) 6.25 kg
92. A sample of the personnel files of eight male employees revealed that, during
a six-month period, they lost the following number of days due to illness: 2, 0, 6, 3,
10, 4, 1 and 2. What is the mean deviation (in days)?
A) 1
B) 0
C) 3 1/8
D) 2 3/8
93. A sample of the monthly amounts spent for food by families of four receiving
food stamps approximates a symmetrical distribution. The sample mean is $150
and the standard deviation is $20. Using the Empirical Rule, about 95 percent of
the monthly food expenditures are between what two amounts?
A) $100 and $200
B) $85 and $105
C) $205 and $220
D) $110 and $190
94. The ages of all the patients in the isolation ward of the hospital are 38, 26, 13,
41 and 22. What is the population variance?
A) 106.8
B) 91.4
C) 240.3
D) 42.4
96. A population consists of all the weights of all defensive tackles on Sociable
University's football team. They are: Johnson, 204 pounds; Patrick, 215 pounds;
Junior, 207 pounds; Kendron, 212 pounds; Nicko, 214 pounds; and Cochran, 208
pounds. What is the population standard deviation (in pounds)?
97. The weights (in grams) of the contents of several small bottles are 4, 2, 5, 4, 5,
2 and 6. What is the sample variance?
A) 6.92
B) 4.80
C) 1.96
D) 2.33
98. Each person who applies for an assembly job at Robert's Electronics is given a
mechanical aptitude test. One part of the test involves assembling a plug-in unit
based on numbered instructions. A sample of the length of time it took 42 persons
to assemble the unit was organized into the following frequency distribution.
Length of Time (in minutes) Number
1 up to 4 4
4 up to 7 8
7 up to 10 14
10 up to 13 9
13 up to 16 5
16 up to 19 2
99. The distribution of a sample of the outside diameters of PVC gas pipes
approximates a symmetrical, bell-shaped distribution. The arithmetic mean is 14.0
inches, and the standard deviation is 0.1 inches. About 68 percent of the outside
diameters lie between what two amounts?
A) 13.5 and 14.5 inches
B) 13.0 and 15.0 inches
C) 13.9 and 14.1 inches
D) 13.8 and 14.2 inches
101. If the sample variance for a frequency distribution consisting of hourly wages
was computed to be 10, what is the sample standard deviation?
A) $1.96
B) $4.67
C) $3.16
D) $10.00
102. Based on the Empirical Rule, what percent of the observations will lie above
the mean plus two standard deviations?
A) 95%
B) 5%
C) 68%
D) 2.5%
103. Samples of the wires coming off the production line were tested for tensile
strength. The statistical results (in PSI) were:
According to the Empirical Rule, the middle 95 percent of the wires tested between
approximately what two values?
A) 450 and 550
B) 460 and 540
C) 420 and 580
D) 380 and 620
104. What measure of central location uses all of the observations in its
calculation? ______________
105. What is the class with the largest number of observations called?
______________
107. The value that occurs most often in a set of data is called the _____
108. The weekly sales from a sample of ten computer stores yielded a mean of
$25,900; a median $25,000 and a mode of $24,500. What is the shape of the
distribution? ___________________
109. Which measure of central location requires that the data be ranked before it is
possible to determine it? _____________
112. If the n-th root is taken of the product of ""n"" values, what is the result?
_____________________
114. A sample revealed that the ages of musicians playing in small local combos
are 36, 29, 37, 32, 36 and 75. What is the most appropriate measure of central
location to represent the ages of the musicians? ______________
115. What measure of central location cannot be determined if the distribution has
an open-ended class? ______________________.
119. What is the relationship between the mean and median in a negatively
skewed distribution? ________________
120. What is the relationship between the median and the mode in a positively
skewed distribution? _________________
121. Five students were given a page of problems with the instructions to solve as
many as they could in one hour. Five students solved the following number of
problems: 12, 10, 8, 6 and 4. What is the arithmetic mean number of minutes
required per problem?________
122. David Electronics had a profit of $10 million in 2002. Profit doubled from
2002 to 2003 and profit increased eight fold from 2003 to 2004. What was the
annual geometric mean rate of growth from 2002 to 2004? ______________
123. What is the difference between the largest and the smallest values in a set of
data? __________
124. When is the only time the variance equals the standard deviation?
________________
125. According to the Empirical Rule, what percent of the observations lie within
plus and minus one standard deviation of the mean? ________
126. What is the positive square root of the standard deviation? _________
127. The capacities of several metal containers are: 38, 20, 37, 64, and 27 liters.
What is the range in liters? _____
130. A study measured the number of hours a light bulb will operate before it
burns out. If the variance of this distribution were computed, what would be the
unit of measure? _____________________
139. For Unleaded gas, which measure of central location would be the lowest?
140. For Super Unleaded gas, which measure of central location would be the
highest? _____________
142. What is the approximate mode for the grouped data? ______________
143. What is the approximate mean for the grouped data? _______________
144. What is the approximate median for the grouped data? _____________
Multiple Choice
Fill-in-the-Blank
149. Based on the values of the arithmetic mean, median, and mode, what is the
most likely shape of the distribution? __________________
Essay
150. What are the similarities and differences between the mean, the median, and
the mode?
151. What are the similarities and differences between the range and the standard
deviation?
152. When reporting descriptive statistics for a variable, why should the report
include measures of location and dispersion?