CNSPulse

THE TYRANNY OF THE P-VALUE: EFFECT SIZE MATTERS

Leslie Citrome — New York Medical College

2026 ASCP Annual Meeting

The “tyranny of the P” can lead researchers astray, allow irrelevant findings to be published, and confuse clinicians eager for guidance as to the usefulness of potential interventions. In order to quantify the clinical importance of a statistically significant result, we need to calculate the effect size. Although there are several absolute and relative effect size measures available, Number Needed to Treat (NNT) is arguably the most intuitive, and is simple to calculate. Advantages and disadvantages of the NNT metric are discussed.

Learning Objective 1: Understand how the P-value can be misused.

Learning Objective 2: Be able to calculate Number Needed to Treat.

References

  1. Citrome L. Compelling or irrelevant? Using number needed to treat can help decide. Acta Psychiatr Scand. 2008 Jun;117(6):412-9. doi: 10.1111/j.1600-0447.2008.01194.x. PMID: 18479317.
  2. Citrome L. Relative vs. absolute measures of benefit and risk: what’s the difference? Acta Psychiatr Scand. 2010 Feb;121(2):94-102. doi: 10.1111/j.1600-0447.2009.01449.x. Epub 2009 Aug 19. PMID: 19694632.