title: Understanding results: P-values, confidence intervals, and number need to treat.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: Department of Urology, University of California, San Francisco, CA, USA.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Flechner
authors.forename: Timothy Y
authors.initials: TY
authors.lastname: Tseng