Principles of Study Design
John Frain · 2025
Systemic error in study design may occur through the method of sampling, by the test used or by encouraging one outcome or answer above others. When testing the efficacy of an intervention (e.g. a treatment), a randomised controlled trial (RCT) is the most suitable design to minimise bias. The RCT is often cited as the ‘gold standard’ in medical research. It is essential to understand the strengths and weaknesses of each type of study design, both for our own research and when retrieving a study to answer a clinical question about a patient. Randomisation aims to create two or more groups similar in respect to all factors which might affect the outcome except for the intervention. It is an attempt to deal with confounding variables within a population. One of the great achievements of evidence-based healthcare is evidence synthesis. This is exemplified most significantly by the systematic review.