Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition

Published by McGraw-Hill Education
ISBN 10: 0078136334
ISBN 13: 978-0-07813-633-7

Chapter 1 - The Nature of Probability and Statistics - 1-4 Experimental Design - Extending the Concepts - Page 26: 45


A confounding variable is one that influences the dependent or outcome variable but was not separated from the independent variable. As seen from the statistical study shown in the step by step section below, there are confounding variables which may affect the outcome together with the dosage used by the designer of the experiment. As biological processes are usually complicated, the are other factors (such as race, gender, age, health conditions, daily diet, hobbies) which may affect the outcomes. A carefully designed experiment will use control groups to eliminate all possible confounding factors.

Work Step by Step

According to a pilot study of 20 people conducted at the University of Minnesota, daily doses of a compound called arabinogalactan over a period of 6 months resulted in a significant increase in the beneficial lactobacillus species of bacteria.
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