Five-Minute Check (over Lesson 8–8)
Main Idea
Example 1: Changing the Interval of Graphs
Example 2: Identify Biased Displays
Example 3: Misleading Statistics
• Recognize when statistics and graphs are
misleading.
Changing the Interval of Graphs
BUSINESS The line graphs below show the last 10
weeks of sales for the Crumby Cookie Bakery. Do the
graphs show the same data? If so, explain how the
graphs differ. Which graph makes it appear that the
bakery's sales declined only slightly?
Changing the Interval of Graphs
Answer: The graphs show the same data, but the scale
of Graph A has greater intervals and a greater
range. Graph A makes it appear that the
bakery's sales declined only slightly.
SOCCER The graphs show
the number of wins by four
different soccer teams. Do the
graphs show the same data?
If so, explain how they differ.
A. same data; intervals on the
graphs are different
D. different data
0%
A
B
C
D 0%
D
A
0%
C
C. same data; scale in Graph B
is not consistent
1.
2.
3.
0%4.
B
B. same data; data in Graph A is
graphed incorrectly
Identify Biased Displays
TECHNOLOGY A Web site
e-mailed 1,000 of its members
to determine its members’
favorite hobbies. The results
are shown in the histogram.
Identify any sampling errors
and explain why the sample
and display might be biased.
Identify Biased Displays
Answer: The sample is a biased convenience sample.
Members of a Web site probably enjoy
computers more than other activities. The
display is biased because the data used to
create the display came from a biased sample.
ANIMALS A pet store owner sent a mail
survey to 200 of his customers to what
kind of pet is most popular. The results
are shown in the graph. Using this
information, which of the following
statements is true?
The sample is biased because it is a
voluntary response sample.
D.
The display is unbiased because it
came from an unbiased sample.
The sample is unbiased because it
represents all pet owners.
0%
A
C.
1.
2.
3.
0% 4.
0%
A
B
C
D
0%
D
B.
C
The sample is unbiased since it was
mailed.
B
A.
Misleading Statistics
GRADES Michael and Melissa both claim to be
earning a C average—70% to 79%—in their Latin
class. One student is wrong. Which one? Explain
how he or she is using a misleading statistic.
Michael
Melissa
mean 53.4%
median 70%
71.9%
70%
Misleading Statistics
Answer: Michael is wrong. He claimed to be earning a
C average because his median was 70%. But
his mean, or average, is much less than 70%.
RETAIL SALES Two different
grocery stores each claim to
have the lowest average prices.
Use the table below to
determine which store really
has the lowest average prices.
A. Store A
1.
2.
3.
0%
B
0%
A
C. Both stores have the same
average price.
A
B
C
0%
C
B. Store B
End of the Lesson
Five-Minute Check (over Lesson 8–8)
Image Bank
Math Tools
Line Plots
(over Lesson 8-8)
B.
not valid, biased sample
C.
valid, biased sample
D.
not valid, unbiased sample
A
0%
1.
2.
3.
0%
4.
A
B
C
0%
D
0%
D
valid, unbiased sample
C
A.
B
A mathematics class decided to find out if students enjoy gym
class. The football team had practice that day so they decided
to survey them. Fifty-eight of the sixty players all enjoyed gym
class, so the class determined that almost all students enjoy
gym class. Determine whether the conclusion is valid. Justify
your answer.
(over Lesson 8-8)
Mr. Brown’s class conducted a survey to determine how
many students wanted to listen to music in class. The
survey was given to every student in Mr. Brown’s Algebra
class. Describe the sample and determine if the sampling
method is valid.
C.
unbiased convience sample, invalid
D.
biased sample, valid
0%
1.
2.
3.
0%
4.
A
B
C
0%D
0%
D
unbiased convience sample, valid
C
B.
B
biased convience sample, invalid
A
A.
(over Lesson 8-8)
Fritz wants to conduct a survey to determine if the San
Francisco 49ers is the favorite team at school. Which of the
following methods is the best way for him to choose a random
sample at his school?
Select students from the football
team.
Select ten students from each
class.
D.
Select students from the girls’
volleyball team.
0%
A
C.
0%
1.
2.
3.
0%
4.
A
B
C0%
D
D
B.
C
Select students from the 49er
Cheering Club.
B
A.