Solutions Manual for Statistics 5th Edition Agresti
PART ONE: GATHERING AND EXPLORING DATA (Questions 1-45)
Chapter 1: Statistics - The Art and Science of Learning from Data
Question 1
A researcher wants to study the average height of all students at a university with
20,000 students. She measures the heights of 500 randomly selected students.
What is the population in this study?
A) The 500 students measured
B) The 20,000 students at the university
C) The average height of the 500 students
D) The measuring instrument used
Answer: B
Rationale: The population is the entire group of interest—all 20,000 university
students. The 500 students are the sample, a subset selected from the
population. The average height of the sample is a statistic, and the measuring
instrument is a tool, not the population .
,Question 2
Continuing with the height study above, the average height of the 500 students is
68.5 inches. This value is a:
A) Parameter
B) Population
C) Statistic
D) Variable
Answer: C
Rationale: A statistic is a numerical summary computed from sample data. Since
the 68.5 inches comes from the sample of 500 students (not the entire population
of 20,000), it is a statistic. If we computed the average using all 20,000 students,
that would be a parameter .
Question 3
Which of the following is an example of inferential statistics?
A) Calculating the mean age of 50 survey respondents
B) Creating a bar chart showing favorite ice cream flavors
,C) Using sample data to estimate the percentage of all voters who support a
candidate
D) Listing all individual data points in a dataset
Answer: C
Rationale: Inferential statistics involves using sample data to draw conclusions
about a larger population. Estimating voter support from a sample is inference.
Options A, B, and D are descriptive statistics—they simply summarize or present
the data at hand without generalization.
Question 4
A political pollster surveys 1,200 registered voters and finds that 52% support a
particular candidate. The poll has a margin of error of ±3%. This margin of error
reflects:
A) The pollster's personal opinion about the candidate
B) The variability expected due to sampling only a portion of the population
C) The number of people who refused to answer the poll
D) The exact percentage of all voters who support the candidate
Answer: B
, Rationale: Margin of error quantifies the expected sampling variability—how
much the sample statistic might differ from the true population parameter due to
random chance. It does not reflect non-sampling errors like non-response or the
pollster's opinion .
Question 5
A study follows a group of 500 adults over 10 years to examine the relationship
between exercise habits and heart disease. The researchers do not assign exercise
routines; they simply observe participants' natural behaviors. This is an example
of:
A) An experimental study
B) A randomized controlled trial
C) An observational study
D) A census
Answer: C
Rationale: In an observational study, researchers observe subjects and measure
variables without assigning treatments or interventions. Since the researchers are
not assigning exercise routines but simply observing existing habits, this is
observational. Experimental studies involve active manipulation .
PART ONE: GATHERING AND EXPLORING DATA (Questions 1-45)
Chapter 1: Statistics - The Art and Science of Learning from Data
Question 1
A researcher wants to study the average height of all students at a university with
20,000 students. She measures the heights of 500 randomly selected students.
What is the population in this study?
A) The 500 students measured
B) The 20,000 students at the university
C) The average height of the 500 students
D) The measuring instrument used
Answer: B
Rationale: The population is the entire group of interest—all 20,000 university
students. The 500 students are the sample, a subset selected from the
population. The average height of the sample is a statistic, and the measuring
instrument is a tool, not the population .
,Question 2
Continuing with the height study above, the average height of the 500 students is
68.5 inches. This value is a:
A) Parameter
B) Population
C) Statistic
D) Variable
Answer: C
Rationale: A statistic is a numerical summary computed from sample data. Since
the 68.5 inches comes from the sample of 500 students (not the entire population
of 20,000), it is a statistic. If we computed the average using all 20,000 students,
that would be a parameter .
Question 3
Which of the following is an example of inferential statistics?
A) Calculating the mean age of 50 survey respondents
B) Creating a bar chart showing favorite ice cream flavors
,C) Using sample data to estimate the percentage of all voters who support a
candidate
D) Listing all individual data points in a dataset
Answer: C
Rationale: Inferential statistics involves using sample data to draw conclusions
about a larger population. Estimating voter support from a sample is inference.
Options A, B, and D are descriptive statistics—they simply summarize or present
the data at hand without generalization.
Question 4
A political pollster surveys 1,200 registered voters and finds that 52% support a
particular candidate. The poll has a margin of error of ±3%. This margin of error
reflects:
A) The pollster's personal opinion about the candidate
B) The variability expected due to sampling only a portion of the population
C) The number of people who refused to answer the poll
D) The exact percentage of all voters who support the candidate
Answer: B
, Rationale: Margin of error quantifies the expected sampling variability—how
much the sample statistic might differ from the true population parameter due to
random chance. It does not reflect non-sampling errors like non-response or the
pollster's opinion .
Question 5
A study follows a group of 500 adults over 10 years to examine the relationship
between exercise habits and heart disease. The researchers do not assign exercise
routines; they simply observe participants' natural behaviors. This is an example
of:
A) An experimental study
B) A randomized controlled trial
C) An observational study
D) A census
Answer: C
Rationale: In an observational study, researchers observe subjects and measure
variables without assigning treatments or interventions. Since the researchers are
not assigning exercise routines but simply observing existing habits, this is
observational. Experimental studies involve active manipulation .
