Methods for Assessing the Credibility of Clinical Trial Outcomes


Credibility—the believability of new findings in the light of current knowledge—is a key issue in the assessment of clinical trial outcomes. Yet, despite the growth of evidence-based medicine, credibility is usually dealt with in a broad-brush and qualitative fashion. This paper describes how Bayesian methods lead to quantitative credibility assessments that take explicit account of prior insights and experience. A simple technique based on the concept of the critical prior interval (CPI) is presented, which allows rapid credibility assessment of trial outcomes reported in the standard format of odds ratios and 95% confidence intervals. The critical prior interval is easily determined via a graph, and provides clinicians with an explicit and objective baseline on which to base their assessment of credibility. The use of the critical prior interval is demonstrated through several working examples.

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Corresponding author

Correspondence to Robert A. J. Matthews.

Additional information

Based on a presentation from the DIA Workshop “Statistical Methodology in Clinical R&D,” April 2–4, 2001, Vienna, Austria.

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Matthews, R.A.J. Methods for Assessing the Credibility of Clinical Trial Outcomes. Ther Innov Regul Sci 35, 1469–1478 (2001).

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Key Words

  • Credibility
  • Critical prior interval
  • Bayesian methods