Answer
Observational study.
Work Step by Step
The subjects are not subjected to a treatment, but it is only is observed if they are belted or not. 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 23 - Comparing Two Proportions - Apply Your Knowledge - Page 548: 23.4a
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