Experimental design and statistics in orthopaedic research

An understanding of the fundamentals of experimental design and statistical analysis is essential in the undertaking of any successful clinical research. There is no substitute for methodological quality but even well-designed studies can be let down by a poor examination of the data and incorrect application of statistical methods. The purpose of this article was to help provide an overview of the basic principles used in the design of clinical research. It covers both observational and experimental studies including case control studies, cohort studies and the gold standard randomized control trials (RCTs). It highlights the importance of sample power, type I and type II error, study randomization and blinding, and the effects of bias on outcome measures. The article uses examples from the published orthopaedic literature to stress the importance of these variables and the need for caution when interpreting the results. As a reader the most important thing is to maintain a critical eye with particular focus on the experimental design and study power and any interpretation of the data must be coupled with an awareness of the potential pitfalls.