INSTRUCTOR’S
SOLUTIONS MANUAL
TONI GARCIA
ELEMENTARY
STATISTICS
NINTH EDITION
Neil A. Weiss
, Contents
Chapter 1 The Nature of Statistics 1
Chapter 2 Organizing Data 21
Chapter 3 Descriptive Measures 125
Chapter 4 Descriptive Methods in Regression
and Correlation 213
Chapter 5 Probability and Random Variables 295
Chapter 6 The Normal Distribution 359
Chapter 7 The Sampling Distribution of the
Sample Mean 413
Chapter 8 Confidence Intervals for One
Population Mean 473
Chapter 9 Hypothesis Tests for One
Population Mean 525
Chapter 10 Inferences for Two Population Means 567
Chapter 11 Inferences for Population Proportions 627
Chapter 12 Chi-Square Procedures 661
Chapter 13 Anaylsis of Variance (ANOVA) 713
Chapter 14 Inferential Methods in Regression
and Correlation 771
, 1
CHAPTER 1 SOLUTIONS
Exercises 1.1
1.1 (a) The population is the collection of all individuals or items under
consideration in a statistical study.
(b) A sample is that part of the population from which information is
obtained.
1.2 The two major types of statistics are descriptive and inferential
statistics. Descriptive statistics consists of methods for organizing and
summarizing information. Inferential statistics consists of methods for
drawing and measuring the reliability of conclusions about a population
based on information obtained from a sample of the population.
1.3 Descriptive methods are used for organizing and summarizing information and
include graphs, charts, tables, averages, measures of variation, and
percentiles.
1.4 Descriptive statistics are used to organize and summarize information from a
sample before conducting an inferential analysis. Preliminary descriptive
analysis of a sample may reveal features of the data that lead to the
appropriate inferential method.
1.5 (a) An observational study is a study in which researchers simply observe
characteristics and take measurements.
(b) A designed experiment is a study in which researchers impose treatments
and controls and then observe characteristics and take measurements.
1.6 Observational studies can reveal only association, whereas designed
experiments can help establish causation.
1.7 This study is inferential. Data from a sample of Americans are used to make
an estimate of (or an inference about) average TV viewing time for all
Americans.
1.8 This study is descriptive. It is a summary of the average salaries in
professional baseball, basketball, and football for 2005 and 2011.
1.9 This study is descriptive. It is a summary of information on all homes sold
in different cities for the month of September 2012.
1.10 This study is inferential. National samples are used to make estimates of
(or inferences about) drug use throughout the entire nation.
1.11 This study is descriptive. It is a summary of the annual final closing
values of the Dow Jones Industrial Average at the end of December for the
years 2004-2013.
1.12 This study is inferential. Survey results were used to make percentage
estimates on which college majors were in demand among U.S firms for all
graduating college students.
1.13 (a) This study is inferential. It would have been impossible to survey all
U.S. adults about their opinions on Darwinism. Therefore, the data
must have come from a sample. Then inferences were made about the
opinions of all U.S. adults.
(b) The population consists of all U.S. adults. The sample consists only
of those U.S. adults who took part in the survey.
1.14 (a) The population consists of all U.S. adults. The sample consists of the
1000 U.S. adults who were surveyed.
(b) The percentage of 50% is a descriptive statistic since it describes the
opinion of the U.S. adults who were surveyed.
1.15 (a) The statement is descriptive since it only tells what was said by the
respondents of the survey.
Copyright © 2016 Pearson Education, Inc.
, 2 Chapter 1
(b) Then the statement would be inferential since the data has been used to
provide an estimate of what all Americans believe.
1.16 (a) To change the study to a designed experiment, one would start with a
randomly chosen group of men, then randomly divide them into two
groups, an experimental group in which all of the men would have
vasectomies and a control group in which the men would not have them.
This would enable the researcher to make inferences about vasectomies
being a cause of prostate cancer.
(b) This experiment is not feasible, since, in the vasectomy group there
would be men who did not want one, and in the control group there would
be men who did want one. Since no one can be forced to participate in
the study, the study could not be done as planned.
1.17 Designed experiment. The researchers did not simply observe the two groups
of children, but instead randomly assigned one group to receive the Salk
vaccine and the other to get a placebo.
1.18 Observational study. The researchers at Harvard University and the National
Institute of Aging simply observed the two groups.
1.19 Observational study. The researchers simply collected data from the men and
women in the study with a questionnaire.
1.20 Designed experiment. The researchers did not simply observe the two groups
of women, but instead randomly assigned one group to receive aspirin and the
other to get a placebo.
1.21 Designed experiment. The researchers did not simply observe the three
groups of patients, but instead randomly assigned some patients to receive
optimal pharmacologic therapy, some to receive optimal pharmacologic therapy
and a pacemaker, and some to receive optimal pharmacologic therapy and a
pacemaker-defibrillator combination.
1.22 Observational studies. The researchers simply collected available
information about the starting salaries of new college graduates.
1.23 (a) This statement is inferential since it is a statement about all
Americans based on a poll. We can be reasonably sure that this is the
case since the time and cost of questioning every single American on
this issue would be prohibitive. Furthermore, by the time everyone
could be questioned, many would have changed their minds.
(b) To make it clear that this is a descriptive statement, the new
statement could be, “Of 1032 American adults surveyed, 73% favored a
law that would require every gun sold in the United States to be test-
fired first, so law enforcement would have its fingerprint in case it
were ever used in a crime.” To rephrase it as an inferential
statement, use “Based on a sample of 1032 American adults, it is
estimated that 73% of American adults favor a law that would require
every gun sold in the United States to be test-fired first, so law
enforcement would have its fingerprint in case it were ever used in a
crime.”
1.24 Descriptive statistics. The U.S. National Center for Health Statistics
collects death certificate information from each state, so the rates shown
reflect the causes of all deaths reported on death certificates, not just a
sample.
1.25 (a) The population consists of all Americans between the ages of 18 and 29.
(b) The sample consists only of those Americans who took part in the survey.
(c) The statement in quotes is inferential since it is a statement about
all Americans based on a survey.
(d) “Based on a sample of Americans between the ages of 18 and 29, it is
estimated that 59% of Americans oppose medical testing on animals.”
Copyright © 2016 Pearson Education, Inc.
SOLUTIONS MANUAL
TONI GARCIA
ELEMENTARY
STATISTICS
NINTH EDITION
Neil A. Weiss
, Contents
Chapter 1 The Nature of Statistics 1
Chapter 2 Organizing Data 21
Chapter 3 Descriptive Measures 125
Chapter 4 Descriptive Methods in Regression
and Correlation 213
Chapter 5 Probability and Random Variables 295
Chapter 6 The Normal Distribution 359
Chapter 7 The Sampling Distribution of the
Sample Mean 413
Chapter 8 Confidence Intervals for One
Population Mean 473
Chapter 9 Hypothesis Tests for One
Population Mean 525
Chapter 10 Inferences for Two Population Means 567
Chapter 11 Inferences for Population Proportions 627
Chapter 12 Chi-Square Procedures 661
Chapter 13 Anaylsis of Variance (ANOVA) 713
Chapter 14 Inferential Methods in Regression
and Correlation 771
, 1
CHAPTER 1 SOLUTIONS
Exercises 1.1
1.1 (a) The population is the collection of all individuals or items under
consideration in a statistical study.
(b) A sample is that part of the population from which information is
obtained.
1.2 The two major types of statistics are descriptive and inferential
statistics. Descriptive statistics consists of methods for organizing and
summarizing information. Inferential statistics consists of methods for
drawing and measuring the reliability of conclusions about a population
based on information obtained from a sample of the population.
1.3 Descriptive methods are used for organizing and summarizing information and
include graphs, charts, tables, averages, measures of variation, and
percentiles.
1.4 Descriptive statistics are used to organize and summarize information from a
sample before conducting an inferential analysis. Preliminary descriptive
analysis of a sample may reveal features of the data that lead to the
appropriate inferential method.
1.5 (a) An observational study is a study in which researchers simply observe
characteristics and take measurements.
(b) A designed experiment is a study in which researchers impose treatments
and controls and then observe characteristics and take measurements.
1.6 Observational studies can reveal only association, whereas designed
experiments can help establish causation.
1.7 This study is inferential. Data from a sample of Americans are used to make
an estimate of (or an inference about) average TV viewing time for all
Americans.
1.8 This study is descriptive. It is a summary of the average salaries in
professional baseball, basketball, and football for 2005 and 2011.
1.9 This study is descriptive. It is a summary of information on all homes sold
in different cities for the month of September 2012.
1.10 This study is inferential. National samples are used to make estimates of
(or inferences about) drug use throughout the entire nation.
1.11 This study is descriptive. It is a summary of the annual final closing
values of the Dow Jones Industrial Average at the end of December for the
years 2004-2013.
1.12 This study is inferential. Survey results were used to make percentage
estimates on which college majors were in demand among U.S firms for all
graduating college students.
1.13 (a) This study is inferential. It would have been impossible to survey all
U.S. adults about their opinions on Darwinism. Therefore, the data
must have come from a sample. Then inferences were made about the
opinions of all U.S. adults.
(b) The population consists of all U.S. adults. The sample consists only
of those U.S. adults who took part in the survey.
1.14 (a) The population consists of all U.S. adults. The sample consists of the
1000 U.S. adults who were surveyed.
(b) The percentage of 50% is a descriptive statistic since it describes the
opinion of the U.S. adults who were surveyed.
1.15 (a) The statement is descriptive since it only tells what was said by the
respondents of the survey.
Copyright © 2016 Pearson Education, Inc.
, 2 Chapter 1
(b) Then the statement would be inferential since the data has been used to
provide an estimate of what all Americans believe.
1.16 (a) To change the study to a designed experiment, one would start with a
randomly chosen group of men, then randomly divide them into two
groups, an experimental group in which all of the men would have
vasectomies and a control group in which the men would not have them.
This would enable the researcher to make inferences about vasectomies
being a cause of prostate cancer.
(b) This experiment is not feasible, since, in the vasectomy group there
would be men who did not want one, and in the control group there would
be men who did want one. Since no one can be forced to participate in
the study, the study could not be done as planned.
1.17 Designed experiment. The researchers did not simply observe the two groups
of children, but instead randomly assigned one group to receive the Salk
vaccine and the other to get a placebo.
1.18 Observational study. The researchers at Harvard University and the National
Institute of Aging simply observed the two groups.
1.19 Observational study. The researchers simply collected data from the men and
women in the study with a questionnaire.
1.20 Designed experiment. The researchers did not simply observe the two groups
of women, but instead randomly assigned one group to receive aspirin and the
other to get a placebo.
1.21 Designed experiment. The researchers did not simply observe the three
groups of patients, but instead randomly assigned some patients to receive
optimal pharmacologic therapy, some to receive optimal pharmacologic therapy
and a pacemaker, and some to receive optimal pharmacologic therapy and a
pacemaker-defibrillator combination.
1.22 Observational studies. The researchers simply collected available
information about the starting salaries of new college graduates.
1.23 (a) This statement is inferential since it is a statement about all
Americans based on a poll. We can be reasonably sure that this is the
case since the time and cost of questioning every single American on
this issue would be prohibitive. Furthermore, by the time everyone
could be questioned, many would have changed their minds.
(b) To make it clear that this is a descriptive statement, the new
statement could be, “Of 1032 American adults surveyed, 73% favored a
law that would require every gun sold in the United States to be test-
fired first, so law enforcement would have its fingerprint in case it
were ever used in a crime.” To rephrase it as an inferential
statement, use “Based on a sample of 1032 American adults, it is
estimated that 73% of American adults favor a law that would require
every gun sold in the United States to be test-fired first, so law
enforcement would have its fingerprint in case it were ever used in a
crime.”
1.24 Descriptive statistics. The U.S. National Center for Health Statistics
collects death certificate information from each state, so the rates shown
reflect the causes of all deaths reported on death certificates, not just a
sample.
1.25 (a) The population consists of all Americans between the ages of 18 and 29.
(b) The sample consists only of those Americans who took part in the survey.
(c) The statement in quotes is inferential since it is a statement about
all Americans based on a survey.
(d) “Based on a sample of Americans between the ages of 18 and 29, it is
estimated that 59% of Americans oppose medical testing on animals.”
Copyright © 2016 Pearson Education, Inc.
