title: Reliability and validity in a nutshell.
abstract: OBJECTIVE
  To explore and explain the different concepts of reliability and validity as they are related to measurement instruments in social science and health care.
  
  
  BACKGROUND
  There are different concepts contained in the terms reliability and validity and these are often explained poorly and there is often confusion between them.
  
  
  METHODS
  To develop some clarity about reliability and validity a conceptual framework was built based on the existing literature.
  
  
  RESULTS
  The concepts of reliability, validity and utility are explored and explained.
  
  
  CONCLUSIONS
  Reliability contains the concepts of internal consistency and stability and equivalence. Validity contains the concepts of content, face, criterion, concurrent, predictive, construct, convergent (and divergent), factorial and discriminant. In addition, for clinical practice and research, it is essential to establish the utility of a measurement instrument.
  
  
  CONCLUSIONS
  To use measurement instruments appropriately in clinical practice, the extent to which they are reliable, valid and usable must be established.
authors.affiliation: Research Centre for Occupation and Mental Health, York St John University, York YO31 7EX, UK. k.bannigan@yorksj.ac.uk
authors.forename: Katrina
authors.initials: K
authors.lastname: Bannigan
authors.forename: Roger
authors.initials: R
authors.lastname: Watson
mesh_terms: D003695:Delivery of Health Care; D015203:Reproducibility of Results