SCIENTIFIC THINKING In a study to examine the effectiveness of a new acne cream, participants were assigned to one of two groups: those who would be asked to use the cream for three months and those who would not use any treatment. Participants would be asked to keep a journal rating how bad they think their acne is on a scale of 1–10 each week. What are the well-designed aspects of this study? What are the limitations? How would you improve the design of this study to address these limitations?

Verified step by step guidance

1. Identify the well-designed aspects of the study: The study uses a control group (those not using any treatment) which allows for comparison to see if the cream actually has an effect on acne. Participants are also asked to keep a weekly journal, providing regular and consistent data points for analysis.
2. Recognize the limitations of the study: The study relies on subjective self-assessment (rating acne severity on a scale of 1-10), which can vary greatly between individuals and may not accurately reflect actual changes in acne condition. There is no mention of random assignment, which is crucial to ensure that the two groups are comparable and that the results are not biased by pre-existing differences.
3. Suggest improvements to address the limitations: Implement random assignment to evenly distribute potential confounding variables between the treatment and control groups. This helps in making the groups comparable and the study's results more reliable.
4. Introduce a more objective method of measuring acne improvement, such as clinical assessments by dermatologists or standardized photographs taken in controlled conditions. This would complement the subjective ratings and provide a more accurate measure of the cream's effectiveness.
5. Increase the robustness of the study by possibly including a larger sample size or extending the duration of the study to observe long-term effects and variations in acne improvement over time.