#### Answer

It is a matched pairs design.

#### Work Step by Step

The twins are randomly given one of the two treatments, so the researchers can check at each pair of people what effects each vaccine had. Therefore it is a matched pairs design.

Published by
Pearson

ISBN 10:
0321836960

ISBN 13:
978-0-32183-696-0

It is a matched pairs design.

You can help us out by revising, improving and updating this answer.

Update this answerAfter you claim an answer you’ll have **24 hours** to send in a draft. An editor
will review the submission and either publish your submission or provide feedback.