Understanding results: P-values, confidence intervals, and number need to treat

Lawrence Flechner, Timothy Y. Tseng

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Objectives: With the increasing emphasis on evidence-based medicine, the urology literature has seen a rapid growth in the number of high-quality randomized controlled trials along with increased statistical rigor in the reporting of study results. P-values, CI, and number needed to treat (NNT) are becoming increasingly common in the literature. This paper seeks to familiarize the reader with statistical measures commonly used in the evidence-based literature. Materials and Methods: The meaning and appropriate interpretation of these statistical measures is reviewed through the use of a clinical scenario. Results: The reader will be better able to understand such statistical measures and apply them to the critical appraisal of the literature. Conclusions: P-values, CI, and NNT each provide a slightly different estimate of statistical truth. Together, they provide a more complete picture of the true effect observed in a study. An understanding of these measures is essential to the critical appraisal of study results in evidence-based medicine.

Original languageEnglish (US)
Pages (from-to)532-535
Number of pages4
JournalIndian Journal of Urology
Issue number4
StatePublished - Oct 2011


  • Confidence intervals
  • evidence-based medicine
  • number needed to treat
  • statistical significance

ASJC Scopus subject areas

  • Urology


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