Answer
Observational study.
Work Step by Step
No treatment was made deliberately on the subjects and data was collected, thus it is an observational study.
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 25 - Two Categorical Variables: The Chi-Square Test - Chapter 25 Exercises - Page 607: 25.46a
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