7th Grade Math

= Step-by-Step Solutions begin on page R1.

Extra Practice begins on page EP2.

Examples 1 and 2 Determine whether each conclusion is valid. Justify your answer.

4. To evaluate the quality of their product, a manufacturer of cell phones
   checks every 50th phone off the assembly line. Out of 200 phones tested,
   4 are defective. The manager concludes that about 2% of the cell phones
   produced will be defective.


5. To determine whether the students will attend an arts festival at the school,
   Oliver surveys his friends in the art club. All of his friends plan to attend,
   so Oliver assumes that all the students at his school will also attend.


6. A magazine asks its readers to complete and return a questionnaire about
   popular television actors. The majority of those who replied liked one
   actor the most, so the magazine decides to write more articles about that
   actor.
   77 To determine what people in California think about a proposed law,
   5,000 people from the state are randomly surveyed. Of the people
   surveyed, 28% are undecided. The legislature concludes that the law
   should not be passed.
   Determine if the sample method is valid. If so, solve the problem.


7. COMMUNICATION The Student Council advisor Method Number
   E-mail 16
   Newsletter 12
   Announcement 5
   Telephone 3

asked every tenth student in the lunch line

how they preferred to be contacted with

school news. The results are shown in the

table. If there are 680 students at the school,

how many can be expected to prefer E-mail?

9. TRAVEL A random sample of people at a mall shows that 22 prefer to take
   a family trip by car, 18 prefer to travel by plane, and 4 prefer to travel by
   bus. Out of 500 people, how many would you expect to say they prefer
   to travel by plane?

B 10. GRAPHIC NOVEL Refer to the graphic novel frame to answer Exercises a–b.

We are conducting

a survey to see

what type of music

the young people in

our area like. Refer

to the beginning

of the chapter.

a. Which strategy gives Jamar and Marisol an appropriate sample for

valid data?

b. What makes the sample appropriate?

Example 3

Lesson 3F Predictions 475

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