Use and misuse of p-values in designed and observational studies: Guide for researchers and reviewers

David A. Ludwig

Research output: Contribution to journalReview articlepeer-review

30 Scopus citations


Analysis of scientific data involves many components, one of which is often statistical testing with the calculation of p-values. However, researchers too often pepper their papers with p-values in the absence of critical thinking about their results. In fact, statistical tests in their various forms address just one question: does an observed difference exceed that which might reasonably be expected solely as a result of sampling error and/or random allocation of experimental material? Such tests are best applied to the results of designed studies with reasonable control of experimental error and sampling error, as well as acquisition of a sufficient sample size. Nevertheless, attributing an observed difference to a specific treatment effect requires critical thinking on the part of the scientist. Observational studies involve data sets whose size is usually a matter of convenience with results that reflect a number of potentially confounding factors. In this situation, statistical testing is not appropriate and p-values may be misleading; other more modern statistical tools should be used instead, including graphic analysis, computer-intensive methods, regression trees, and other procedures broadly classified as bioinformatics, data mining, and exploratory data analysis. In this review, the utility of p-values calculated from designed experiments and observational studies are discussed, leading to the formation of a decision t ree to aid researchers and reviewers in understanding both the benefits and limitations of statistical testing. &

Original languageEnglish (US)
Pages (from-to)675-680
Number of pages6
JournalAviation Space and Environmental Medicine
Issue number7 I
StatePublished - Jul 1 2005


  • Experimental design
  • Inference
  • Observational studies
  • P-values
  • Statistics

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Pollution
  • Medicine(all)


Dive into the research topics of 'Use and misuse of p-values in designed and observational studies: Guide for researchers and reviewers'. Together they form a unique fingerprint.

Cite this