title: Summarizing changes in an entire population: extensions to the quality improvement ratio.
abstract: BACKGROUND
  In an earlier article the use of the Quality Improvement Ratio (QuIR) was proposed as a way to assess whether an intervention improves preventive health practices. With this method, only members of a health plan observed both before and after an intervention are analyzed. Members observed in only one of the two periods are not included in the QuIR analysis. However, since membership in health plans is constantly changing, the QuIR analysis may exclude a substantial proportion of the total number of members studied.
  
  
  METHODS
  To overcome this problem, an extension to the QuIR analysis, termed the Extended QuIR method, has been developed. Members are classified into two separate groups: those with data in both periods and those with data in only a single period. Members providing data in both periods are analyzed using the QuIR. Members studied in only a single period are analyzed using single-period analysis, described in this article. If the results of the two separate tests are consistent, both suggesting an improvement over time or both suggesting a deterioration, then the results of the two tests can be combined into an overall test to assess whether a change over time occurred.
  
  
  CONCLUSIONS
  The Extended QuIR method, which combines the results of two separate analyses, should help clarify the effect of an intervention on improving preventive health practices in the overall population.
authors.affiliation: Truth, LtdSM, Newton, Massachusetts 02459, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Parker
mesh_terms: D006801:Humans; D007255:Information Services; D008329:Managed Care Programs / Q000592:standards* / Q000706:statistics & numerical data; D008403:Mass Screening / Q000706:statistics & numerical data*; D008404:Massachusetts; D015233:Models, Statistical; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*; D010353:Patient Education as Topic; D011314:Preventive Health Services / Q000706:statistics & numerical data*; D011785:Quality Assurance, Health Care / Q000706:statistics & numerical data*; D012107:Research Design; D014600:Utilization Review