Page 193 - Math Course 3 (Book 2)

Understanding Proportions and Ratios

EDUCATION The board of a school system consisting of 22 elemtary schools, 6 middle schools and 4 high
schools is considering three possible weeks for spring break for the upcoming school year. The board sur-
veyed three randomly-chosen teachers from each school. Of the teachers surveyed, 84 chose the first week
of April. Is this sampling method valid? If so, about how many of the 848 teachers in the school district would
choose the first week of April?

A. The survey is invalid because this is a convenience sample.
B. The survey is invalid because this is a voluntary response sample.
C. The survey is valid because this is a simple random sample. Of all
the teachers, 106 would choose the first week of April.
D. The survey is valid because this is a stratified random sample. Of
all the teachers, 742 would choose the first week of April.

Answer

Skill Practice!

Identify each sample as biased or unbiased and describe its type. Explain your reasoning.
1. To determine how many students have pets, all students in one classroom are surveyed.

2. To determine the number of students who plan on attending the Valentine’s Day dance, 20 students are
randomly selected from each grade level.

3. To determine whether customers are satisfied with their meals, a restaurant collects comment cards that
are voluntarily filled out by customers.

4. To determine the most popular color of car, the color of every 12th car that crosses an intersection
is recorded.

5. To determine the most popular major league baseball team among its readers, a sports magazine polled a
random selection of its readers.

6. ANALYZE TABLES The student council would like to sell pizza slices during home basketball games as a
fund-raiser. During a home game with 250 people in attendance, they surveyed every 10th spectator to enter
the gym about their favorite pizza toppings. Their results are shown in the table. Is this sampling method
valid? If so, how many pepperoni pizzas should be ordered if they order 25 pizzas? Explain your reasonings.

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