To succeed in your psychology entrance exams, you must know how to read a clinical study and spot its strengths and weaknesses. Entrance exams often present a short research summary and ask you to identify variables, research methods, and potential biases.
Let us practice with a mock study about exercise and depression.
The Mock Study: Exercise vs. SSRIs
Study Title: The Impact of Aerobic Exercise Compared to SSRIs on Major Depressive Disorder.
Study Design: Researchers conducted a randomized controlled trial (RCT) with 120 participants diagnosed with Major Depressive Disorder. Participants were randomly assigned to one of three groups for 12 weeks:
- Group A: Aerobic exercise (running on a treadmill for 45 minutes, three times a week).
- Group B: Standard medication (a daily SSRI pill).
- Group C: A waitlist control group (received no treatment during the 12 weeks).
Measurement: Depression levels were measured before and after the 12 weeks using a self-reported questionnaire.
Results: Group A (Exercise) and Group B (SSRIs) both showed a significant decrease in depression scores compared to Group C (Waitlist). However, 15 participants dropped out of Group A because they found the exercise too tiring, while only 2 participants dropped out of Group B.
Exam-Style Analysis
When you see a study like this on your exam, you should immediately break it down into its core components. Here is how to analyze it.
1. Identify the Variables
Exams will almost always ask you to identify the variables.
- Independent Variable (IV): The treatment type (Exercise, SSRI, or Waitlist). This is what the researchers manipulate.
- Dependent Variable (DV): The depression score. This is what the researchers measure to see the effect of the IV.
2. Evaluate the Control Group
Group C is a waitlist control group. This helps prove that time alone did not cure the depression. However, a waitlist group does not account for the placebo effect. Because Group A and Group B knew they were receiving a treatment, their hope or expectation of getting better might have lowered their depression scores, rather than the exercise or medication itself.
3. Spot the Biases and Flaws
This is the most critical part of exam prep. You must find the hidden problems in the study design.
- Lack of Participant Blinding: In this study, participants know which group they are in. You cannot hide from a participant that they are running on a treadmill. This lack of blinding can lead to expectation bias.
- Attrition Bias (Dropout Rate): Group A had a high dropout rate (15 people). This is a major flaw. The people who stayed in the exercise group might be naturally more motivated or have less severe depression than those who quit. This skews the final results, making exercise look more effective than it actually is for the average person.
- Self-Report Bias: The dependent variable was measured using a self-reported questionnaire. Participants might exaggerate their improvement to please the researchers, especially in the exercise group where they worked hard. A clinical interview by a blinded psychologist would be a more reliable measurement.
Exam Checklist for Clinical Studies
Memorize this checklist for your entrance exam. When reading any study, ask yourself:
- Is it an RCT? Were participants randomly assigned?
- What are the IV and DV? What is manipulated, and what is measured?
- Is there a control group? Does it account for the placebo effect?
- Is the study blinded? Do the participants or researchers know who is getting the treatment?
- Did people drop out? Is the dropout rate unequal between groups (attrition bias)?
- How is the data collected? Is it objective (like a blood test) or subjective (like a self-report survey)?
By applying this checklist, you will be able to critically evaluate any clinical psychology study presented in your exam.