Variables, variability, and variations research: implications for medical informatics.

Variations research is one important strategy in the quality management movement designed to improve the quality of health care and to control costs. Information systems are being utilized in variations research to provide an array of potential variables, to provide measures of the variability inherent in these variables, and to assist with the study of the linkages of patient and provider characteristics with interventions and outcomes. This article presents a systems model of inputs, processes, and outcomes with explication of factors related to client, provider, and setting as a heuristic strategy for variable specification. The implications of variable specification, the design and measurement of variability, and the key issue of control in variations research are linked with a discussion of the implications for medical informatics.