Page 197 - Math Course 3 (Book 2)

Sampling and Bias

SCHOOL Identify the Sample
The Parent Association surveys the Example
parents of every fifth student on the
school roster to decide whether to
hold a fundraiser.
SCHOOL
Identify the sample as biased or unbiased. The high school Parent Association sent a letter to
Explain your reasoning. the parents of all graduating seniors asking them
to return the enclosed ballot if they had a prefer-
The parents are picked using a systematic method. ence on where the graduation party was to be held.

Identify the sample.
Answer The sample is unbiased.

Identify and Classify a Biased Sample

Example

COMMUNITY

The maintenance chairperson of a neighborhood
association has been asked by the association to
survey the residents of the neighborhood to find Answer The sample is a group of parents
out when to hold a neighborhood clean-up day. of the graduating seniors
The chairperson decides to ask her immediate
neighbors and the neighbors in the houses directly
across the street from her house. Suggest a population from which the sample was
selected.
Identify the sample, and
suggest a population The population is all of the
from which it was Answer parents of the graduating seniors.
selected.

State whether the sample is unbiased (random) or
The sample is the chairperson’s biased. If unbiased, classify it as simple, stratified,
immediate neighbors and the or systematic. If biased, classify it as convenience
Answer neighbors across the street. The or voluntary response.
population is the residents of the
neighborhood. The sample includes only the parents of the grad-
uating seniors who return the ballot. Therefore, the
reported preference is not likely to be representa-
Classify the sample as a convenience sample or a tive of all of the parents.
voluntary response sample.

This is a convenience sample
Answer because the chairperson asked Answer The sample is biased. It is a
only her closest neighbors. voluntary response sample.

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