Name
LESSON
Date
Class
Practice C
7-8 Identifying Sampling Errors and Bias
Determine whether each sample may be biased. Explain.
1. Jemma works at a dairy. She chooses 50 containers of milk at
random to check the quality of the milk.
2. Brian works at a factory that makes light bulbs. He checks the
first 30 light bulbs that are produced one morning in order to
ensure the quality of that day’s production.
Determine whether each survey question may be biased. Explain.
3. What do you think of the proposal to build a world-class sports
arena in our city?
4. How much money do you think the federal government should spend
on protecting our planet’s irreplaceable and precious resources?
Determine whether the claim is valid. Explain.
Supermarket Survey
5. The manager of a supermarket wants to
know what customers think of the service
at the supermarket.
Question: Do you consider the service at the
supermarket to be excellent, good, fair, or
poor?
50
Responses
Sample: Survey cards are available at the
cash registers for customers who wish to
fill them out. One hundred customers
respond.
60
40
30
20
10
0
Excellent
Good
Fair
Poor
Claim: Half of the supermarket’s customers think the service is poor.
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Holt Mathematics
Practice B
7-8 Identifying Sampling Errors and Bias
Practice A
7-8 Identifying Sampling Errors and Bias
LESSON
LESSON
Determine whether each sample may be biased. Explain.
Determine whether each sample may be biased. Explain.
1. Mr. Chu puts the names of all his students in a hat and chooses
12 names without looking. He surveys these students about the
amount of time they spend studying.
1. A group of 30 people at a vegetarian restaurant are surveyed to
find out about the eating habits of people in a town.
The sample is biased. It is likely that people at a vegetarian
restaurant have different eating habits from other people in the town.
The sample is not biased. It is a random sample.
2. A dentist chooses 100 names at random from her database of
patients and asks these patients how many times per day they
brush their teeth.
2. The editor of a computer magazine wants to know how much
time the average American spends surfing the Web. The editor
sends a survey to 2000 people who subscribe to the magazine.
The sample is not biased. It is a random sample.
The sample is biased. People who subscribe to a computer
Determine whether each survey question may be biased.
Explain.
magazine may spend more time surfing the Web than other people.
Determine whether each survey question may be biased. Explain.
3. What is your opinion of the parking nightmare near the ballpark?
The question is biased. It leads people to agree that parking is a problem.
3. Do you prefer the new and improved Tasty-O’s or the original version?
4. Do you prefer apple juice, orange juice, or grape juice?
The question is biased. It leads people to choose the “new and improved” version.
The question is not biased. It doesn’t lead people to choose one option
over another.
Sara wants to know how many minutes
residents of her town spend in their cars
each day. Use the information below and
the graph to answer each question.
4. Which candidate will you vote for in the upcoming mayoral election?
The question is not biased. It does not lead people to give a particular answer.
Survey: Time Spent
in Car Each Day
Alicia wants to know what students at her school
think of the film Hero-Man III. Use the information
below and the graph to answer each question.
30 to 60
minutes
25%
Sample: 60 residents of the town who are
waiting for a bus
More than
60 minutes
Less than
30 minutes
Dislike
15%
Question: What is your opinion of this summer’s
blockbuster hit Hero-Man III?
Like
75%
Claim: A majority of students like the film.
Claim: Most residents of the town spend less
than 30 minutes per day in their car.
5. Is the sample or question biased? Why?
5. Is the sample or question biased? Why?
The question is biased. Students may be more likely to have a
The sample is biased. People waiting for a bus may not drive as much
as others.
good opinion of a film that is described as a “blockbuster hit.”
6. Is Alicia’s claim valid? Why or why not?
6. Is Sara’s claim valid? Why or why not?
No. The claim may not be valid since the question was biased.
No. The claim may not be valid since the sample was biased.
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Movie Survey
No opinion
10%
Sample: 80 students chosen at random from the
school directory
55%
20%
Question: How many minutes per day do
you spend in your car?
Results:
65
Holt Mathematics
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Practice C
7-8 Identifying Sampling Errors and Bias
66
Holt Mathematics
Review for Mastery
7-8 Identifying Sampling Errors and Bias
LESSON
LESSON
Determine whether each sample may be biased. Explain.
A biased sample is one that does not represent the entire population.
1. Jemma works at a dairy. She chooses 50 containers of milk at
random to check the quality of the milk.
Biased Sample
Non-Biased Sample
Example: Mark surveys shoppers at a farmer’s
market to find out how often people in his city
eat fresh fruits and vegetables.
The sample is not biased. It is a random sample.
2. Brian works at a factory that makes light bulbs. He checks the
first 30 light bulbs that are produced one morning in order to
ensure the quality of that day’s production.
Example: Sasha chooses the names of
50 students at random from a school database
and then surveys these students about their
study habits.
Reason: The sample is biased because
shoppers at a farmer’s market may be more
likely to eat fresh fruits and vegetables than
other people.
Reason: The sample is a random sample, so
every member of the population has the same
chance of being surveyed.
The sample is biased. The first 30 light bulbs may not be typical of the
entire day’s production.
A biased question leads people to give a certain answer.
Biased Question
Determine whether each survey question may be biased. Explain.
3. What do you think of the proposal to build a world-class sports
arena in our city?
The question is biased because the arena is described as “world-class.”
4. How much money do you think the federal government should spend
on protecting our planet’s irreplaceable and precious resources?
Non-Biased Question
Example: What do you think of the plan to tear
down the beautiful Third Street Cinema and
replace it with a plain movie theater?
Example: Which of the teams in the National
Football League do you think will win the Super
Bowl this year?
Reason: People may be less likely to support
tearing down a theater if it is described as
“beautiful” and its replacement is described as
“plain.”
Reason: The question does not lead people to
choose one football team over another.
The question is biased because of the words “irreplaceable” and “precious.”
Determine whether each sample may be biased. Explain.
Determine whether the claim is valid. Explain.
Question: Do you consider the service at the
supermarket to be excellent, good, fair, or
poor?
60
Not biased. Every employee has an equal chance of being chosen.
50
Responses
Sample: Survey cards are available at the
cash registers for customers who wish to
fill them out. One hundred customers
respond.
1. Jana chooses 20 names at random from her company’s phone directory and
surveys these employees about their job satisfaction.
Supermarket Survey
5. The manager of a supermarket wants to
know what customers think of the service
at the supermarket.
2. Dan wants to know the number of minutes the average American exercises each
day. He surveys 30 people at his gym.
40
30
Biased. People at a gym may be more likely to exercise more than other people.
20
10
0
Excellent
Good
Fair
Determine whether each survey question may be biased.
Explain.
Poor
3. Would you prefer to see roses, tulips, or dahlias in the hospital’s garden?
Claim: Half of the supermarket’s customers think the service is poor.
Not biased. The question does not lead people to chose one flower over another.
The claim may not be valid. The sample was a self-selected sample.
4. Did you enjoy reading the classic novel Ann of Green Gables?
People who are unhappy with the service at the supermarket may be
Biased. People may be more likely to say they enjoyed a “classic” novel.
more likely to fill out a survey card.
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
67
Copyright © by Holt, Rinehart and Winston.
Holt Mathematics
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
95
68
Holt Mathematics
Holt Mathematics