Example The manufacturer of a new toothpaste claims that the

Example. The manufacturer of a new toothpaste claims that the new product helps whiten teeth. Sixty subjects were randomly selected and had the whitness of their teeth measured during an examination. Each subject used the new toothpaste for four months. The whiteness of their teeth was again measured, and the results of the two measurements were compared. Which of the following statement is true?

A. This is not an experiment since no control group was used.

B. This is an observational study using a completely randomized design.

C. This is an experiment using a completely randomized design.

D. This is an experiment using a matched pair design.

Solution

As the same \"before and after\" results of the same people are compared, then the measurements are paired.

Hence,

OPTION D: This is an experiment using a matched pair design. [ANSWER, D]