Elementary Statistics (12th Edition)

Published by Pearson
ISBN 10: 0321836960
ISBN 13: 978-0-32183-696-0

Chapter 1 - Introduction to Statistics - 1-2 Statistical and Critical Thinking - Basic Skills and Concepts: 2

Answer

Voluntary response is not random and therefore is not included.

Work Step by Step

The voluntary response sample is not included in the study because the sample obtained was not random and may have introduced self-selection bias. Suppose you used sound statistical techniques to analyze voluntary response samples, the results still would not be valid. For this reason the voluntary response sample is not included in the study.
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