McMaster University

McMaster University

Why perform a priori sample size calculation?

We would like to share with you the most recent publication from the MacOrtho team. This paper, titled "Why perform a priori sample size calculation?" has been published in the Canadian Journal of Surgery.

Find the abstract below and click here to access the full-version of the article.

Farrokhyar F, Reddy D, Poolman RW, Bhandari M. Why perform a priori sample size calculation? Can J Surg. 2013 Jun;56(3):207-13.


The application of evidence-based care in the practice of surgery has improved in the past decade (i.e., colorectal surgery, arthroplasty
surgery),1,2 but surgical treatments are still less likely to be studied using full-scale and well-designed randomized controlled trials (RCTs).3 Few surgical RCTs report and justify sample size calculations, and insufficient study power is one of the major shortcomings of many surgical trials. For example,systematic reviews of the surgical RCTs have shown that only 28% of coronary artery bypass grafting surgery trials, 12% of trauma or orthopedic surgery trials,41% of pancreatico-duodenectomy trials and 25% of laparoscopic surgery trials have reported sample size calculations. The findings from underpowered and poorly designed surgical RCTs may be overvalued because their design grants them unwarranted credibility. Moreover, erroneous conclusions generated by these trials may guide clinical practice as clinicians’ decisions may be influenced by the fact that an RCT design was used. This article focuses on the importance, concept and methods of a priori sample size calculation (or power analysis) in surgical RCTs. The underlying methods described for RCTs are equally applied to non-RCT designs.

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