Chapter 6.2, Problem 75E

(a)

To determine

Whether the participants in the experiment subject to placebo effect.

Answer to Problem 75E

Yes, the participants in the experiment subject to placebo effect.

Explanation of Solution

Given information:

34 ten − year − old girls whose parents volunteered them for the study were randomly assigned to two groups.

One group was given fluoride varnish annually for 4 years, along with standard dental hygiene.

Other group followed only the standard dental hygiene regimen.

A placebo is something which is identical to the treatment that the treatment group receives, except that it contains no active ingredients.

The placebo effect is an effect produced by a placebo, which cannot be due to the placebo itself, but caused by the patient’s belief in that treatment.

In this case, the participants in the experiment are subject to the placebo effect.

The participants will know whether they use the fluoride varnish or not, because there is no alternative for those who do not receive fluoride varnish.

Also,

This knowledge might affect the results due to the patient’s belief in the treatment.

For example,

By those children paying more attention to take care of their teeth as compared to those who do not use the fluoride varnish.

(b)

To determine

Alteration of the experiment to make it double − blind.

Answer to Problem 75E

Participants not using fluoride varnish should be given some placebo very identical to fluoride varnish.

The dentist also should not be aware of which treatment the children received.

Explanation of Solution

Given information:

34 ten − year − old girls whose parents volunteered them for the study were randomly assigned to two groups.

One group was given fluoride varnish annually for 4 years, along with standard dental hygiene.

Other group followed only the standard dental hygiene regimen.

In the single − blind experiment, either the individuals who measure or the subjects know which treatment was received.

In the double − blind experiment, neither the subjects nor the individuals who measure know which treatment was received.

In the study, the participants should not be aware of which treatment they receive.

Thus,

We should give the participants who do not use the fluoride varnish some placebo that looks identical to the fluoride varnish.

Also,

We should not inform the participants (or their parents) which treatment is received.

Hence,

It will make the study double − blind.

Then

The dentist who checks the participant’s teeth should not be aware of which treatment should not be aware of which treatment is received.

Otherwise, they could subconsciously or consciously change the measurements in their benefit.

(c)

To determine

Purpose of the random assignment in the experiment.

Answer to Problem 75E

The purpose of random assignment is to be sure that the difference between the two groups after the treatments is due to the treatments themselves.

Explanation of Solution

Given information:

34 ten − year − old girls whose parents volunteered them for the study were randomly assigned to two groups.

One group was given fluoride varnish annually for 4 years, along with standard dental hygiene.

Other group followed only the standard dental hygiene regimen.

The participants are randomly assigned to the treatment groups.

Such that

The different groups are as similar as possible prior to the treatments.

Also,

We can be sure that the difference between the two groups after the treatments is due to treatments themselves.