Answer
Experiment.
Work Step by Step
The subjects were randomly assigned to a group before undergoing a treatment, thus it is an experiment.
The Basic Practice of Statistics 7th Edition
by Moore, David S.; Notz, William I.; Fligner, Michael A.
Published by
W. H. Freeman
ISBN 10:
146414253X
ISBN 13:
978-1-46414-253-6
Chapter 23 - Comparing Two Proportions - Chapter 23 Exercises - Page 557: 23.35a
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