1. A

2. B

3. C

4. D

0% 0%0%0%

A. 309

B. 479

C. 527

D. 637

A survey of high school students said that 63% planned on taking college courses after graduation. About how many of the 837 students in the school are planning on taking college courses?

(over Lesson 8-7)

Main Idea and Vocabulary

Concept Summary: Unbiased Samples

Concept Summary: Biased Samples

Example 1: Determine Validity of Conclusions

Example 2:Determine Validity of Conclusions

Example 3: Real-World Example

• Predict the actions of a larger group by using a sample (2.6.8B) (M7.E.4.1).

• sample-survey of a smaller group• unbiased sample-represents entire population

• simple random sample-each person in population is as likely to be chosen as any other.

• biased sample- one or more parts of population are favored over others.

• convenience sample-population includes members easily accessed.

• voluntary response sample-those who want to participate

Determine Validity of Conclusions

A newspaper asks its readers to answer a poll about whether or not an issue should be on the ballot in an upcoming election. 85% of the readers who responded said they wanted the issue on the ballot, so the newspaper printed an article saying that 85% of people want the issue on the ballot. Determine whether the conclusion is valid. Justify your answer.

Answer: The conclusion is not valid. The population is restricted to readers and it is a voluntary response sample and is biased. The readers of a voluntary response sample do not necessarily represent the entire population.

1. A

2. B

3. C

4. D0% 0%0%0%

A. valid; simple random sample

B. invalid; convenient sample

C. invalid; voluntary response sample

D. cannot determine from information given

A coffee shop asks every tenth customer that comes in the door to identify their favorite coffee drink. 45% of the customers surveyed said that mocha coffee is their favorite drink. The manager of the store concluded that about half of the store’s customers like the mocha coffee. Determine whether the conclusion is valid and justify your answer.

Determine Validity of Conclusions

To award prizes at a sold out baseball game, a computer will pick 10 different seat numbers. Abbey concludes that she has as good a chance as everyone else to win one of the prizes. Determine whether each conclusion is valid. Justify your answer.

Answer: The conclusion is valid. The population is a simple random sample.

1. A

2. B

3. C

4. D0% 0%0%0%

A. valid; simple random sample

B. invalid; convenience sample

C. invalid; voluntary response sample

D. cannot determine from information given

To determine readers’ favorite types of books, a library conducted an online survey. Of those who responded, 26% chose fiction as their favorite type of book. The librarian concluded that a fourth of the books checked out are fiction. Determine whether the conclusion is valid and justify your answer.

VENDING MACHINES An office building manager interviewed 60 employees to determine whether or not a vending machine should be placed in the break room. 45 of the employees said yes and 15 said no. If there are 255 employees in the building, predict how many employees would like a vending machine in the break room.

So, find 75% of 255.

0.75 × 255 = 191.25 75% of 255 = 0.75 × 275

Answer: So, about 191 employees would like a vending machine in the break room.

1. A

2. B

3. C

4. D

0% 0%0%0%

A. 42 students

B. 52 students

C. 53 students

D. 63 students

CLUBS A Spanish teacher is trying to determine if students would be interested in joining a Spanish club. She randomly asked 30 of her students. 18 of the students said yes and 12 said no. If the teacher has 105 students in her Spanish classes, predict how many would like to join a Spanish club.

1. A

2. B

3. C

4. D0% 0%0%0%

A. Select students from the 49er Cheering Club.

B. Select students from the football team.

C. Select ten students from each class.

D. Select students from the girls’ volleyball team.

Fritz wants to conduct a survey to determine if the Pittsburgh Steelers 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?

REVIEW

End of the Lesson

Five-Minute Check (over Lesson 8–7)

Image Bank

Math Tools

Line Plots