Question

Which of the following studies on the effectiveness of a new tooth whitening gel is NOT an experiment?A..B..C..D.

	A.	A dental practice sends coupons for the tooth whitening gel to all their patients. After two months, as patients come in for appointments, they are asked if they have used the product or not. The whiteness of patients’ teeth is assessed by a technician who does not know who used the gel, and users are compared with non-users
	B.	A group of 88 adults is divided at random into two groups. One group is given the tooth whitening gel and the other is given a similar-looking package of gel that has no whitening effect. Both groups are told to use their gel for 6 weeks. At the end of the period, the whiteness of their teeth is assessed by a technician who does not know which gel was used
	C.	A group of 88 adults has their teeth examined and the whiteness of their teeth is assessed using a dental scale. Then, patients who have teeth of similar whiteness are paired, and one member of each pair is given the whitening gel to use; the other person gets a “placebo” gel. At the end of 6 weeks, the whiteness of their teeth is assessed again assessed by a technician who does not know which gel was used, and it’s recorded if their teeth are still equally white or if one member of the pair now has a whiter shade
	D.	A group of 88 adults has their teeth examined and the whiteness of their teeth is assessed using a dental scale. The, all of them are given the whitening gel to use for 6 weeks. At the end of 6 weeks, the whiteness of their teeth is assessed again and, for each participant, it’s recorded if the whiteness of their teeth has changed.

Answer 1

A) A dental practice sends coupons for the tooth whitening gel to all their patients. After two months, as patients come in for appointments, they are asked if they have used the product or not. The whiteness of patients’ teeth is assessed by a technician who does not know who used the gel, and users are compared with non-users.

In all other cases, the researcher interferes (experiments) in the actions of the participants of the study, making it an experiment. In case (A), it is an observational study.