title: Stratified sampling design based on data mining.
abstract: OBJECTIVE
  To explore classification rules based on data mining methodologies which are to be used in defining strata in stratified sampling of healthcare providers with improved sampling efficiency.
  
  
  METHODS
  We performed k-means clustering to group providers with similar characteristics, then, constructed decision trees on cluster labels to generate stratification rules. We assessed the variance explained by the stratification proposed in this study and by conventional stratification to evaluate the performance of the sampling design. We constructed a study database from health insurance claims data and providers' profile data made available to this study by the Health Insurance Review and Assessment Service of South Korea, and population data from Statistics Korea. From our database, we used the data for single specialty clinics or hospitals in two specialties, general surgery and ophthalmology, for the year 2011 in this study.
  
  
  RESULTS
  Data mining resulted in five strata in general surgery with two stratification variables, the number of inpatients per specialist and population density of provider location, and five strata in ophthalmology with two stratification variables, the number of inpatients per specialist and number of beds. The percentages of variance in annual changes in the productivity of specialists explained by the stratification in general surgery and ophthalmology were 22% and 8%, respectively, whereas conventional stratification by the type of provider location and number of beds explained 2% and 0.2% of variance, respectively.
  
  
  CONCLUSIONS
  This study demonstrated that data mining methods can be used in designing efficient stratified sampling with variables readily available to the insurer and government; it offers an alternative to the existing stratification method that is widely used in healthcare provider surveys in South Korea.
authors.affiliation: Technology Management, Economics and Policy Graduate Program, Seoul National University, Seoul, Korea.
authors.forename: Yeonkook J
authors.initials: YJ
authors.lastname: Kim
authors.forename: Yoonhwan
authors.initials: Y
authors.lastname: Oh
authors.forename: Sunghoon
authors.initials: S
authors.lastname: Park
authors.forename: Sungzoon
authors.initials: S
authors.lastname: Cho
authors.forename: Hayoung
authors.initials: H
authors.lastname: Park
keywords: Data Mining; Decision Trees; Sampling Studies