title: Incorporating natural variation into IVF clinic league tables.
abstract: BACKGROUND
  More and more league tables are being published every day to rate the performance of health boards, hospitals and surgeons. However, they do not show the magnitude of uncertainty caused by natural variation.
  
  
  METHODS
  We propose a new method to present league tables in which the ratings are easy to interpret. Instead of just giving one score, we suggest the addition of best-case scenario and worst-case scenario scores. The true performance of a clinic, accounting for natural variation, is most likely to be between the best-case scenario and the worst-case scenario for its rating. These ratings can be computed easily, without any special software.
  
  
  RESULTS
  We illustrate our method based on data of Dutch IVF clinics from 2004. Six (out of 13) clinics shared a 'top of the league' position when considering the best-case scenario.
  
  
  CONCLUSIONS
  There is great uncertainty about the ratings. To show the magnitude of uncertainty, league tables should include the best-case scenario and the worst-case scenario ratings of each clinic.
authors.affiliation: Department of Epidemiology and Biostatistics, 133 Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Oscar
authors.initials: O
authors.lastname: Lemmers
authors.forename: Jan A M
authors.initials: JA
authors.lastname: Kremer
authors.forename: George F
authors.initials: GF
authors.lastname: Borm
mesh_terms: D000554:Ambulatory Care Facilities / Q000592:standards*; D019985:Benchmarking / Q000379:methods*; D015982:Bias; D003627:Data Interpretation, Statistical; D003953:Diagnosis-Related Groups; D005260:Female; D005307:Fertilization in Vitro / Q000592:standards* / Q000706:statistics & numerical data; D006801:Humans; D009426:Netherlands / Q000453:epidemiology; D011247:Pregnancy; D018873:Pregnancy Rate; D019984:Quality Indicators, Health Care / Q000706:statistics & numerical data*