Question

Following the steps given, design a randomized comparative experiment to test whether fluoxetine (the active ingredient in Prozac pills) is effective at reducing depression. The participants are 50 people suffering from depression and the response variable is the change on a standard questionnaire measuring level of depression. (a) Describe how randomization will be used in the design. (b) Describe how a placebo will be used. (c) Describe how to make the experiment double-blind.

Short answer

This experiment could be conducted by randomly assigning the 50 participants into two groups. One group will receive fluoxetine (treatment group), and the other will receive a placebo (control group). The placebo will look the same as the fluoxetine. A third party will code and prepare the pills so that neither the participants nor the researchers interacting with them know which individuals are in which groups (fluoxetine or placebo), making the experiment double-blind.

Step-by-step solution

Understanding the purpose of the experiment

First, note the purpose of the experiment, which is to test if fluoxetine is effective at reducing depression. The participants of the experiment are 50 people with depression. The response variable, which is what you will measure to determine the outcome of the experiment, is the change on a standard questionnaire measuring level of depression.

Applying randomness in design

The randomization in this experiment would involve randomly assigning the 50 participants into two groups. Randomization helps to control for confounding variables. The random assignment can be done by using a method such as flipping a coin or using a computer program. One group will be given the fluoxetine (treatment group) and the other group will be given a placebo (control group). Assigning participants to groups randomly ensures there is no bias in the groupings, and any differences seen in the response variable can be credited to the treatment, not to the selection process.

Application of placebo

A placebo is a substance that appears identical to the actual treatment but has no therapeutic value. For this experiment, half of the participants who will be in the control group will receive the placebo in the form of a pill that looks just like the Prozac pill. This is important because it ensures that any psychological effects that people may experience simply because they believe they are being treated (the placebo effect) happen equally in both the treatment and control groups.

Making the experiment double-blind

A double-blind experiment is one in which neither the participants nor the researchers interacting with the participants know which individuals are in the treatment group and which are in the control group. To achieve this, the pills could be prepared and coded by a third party so that both the researchers and participants will not know who is receiving the fluoxetine and who is receiving the placebo. This prevents bias in reporting and measuring results, and ensures that the study is more reliable and valid.