Objective: The purpose of this article is to discuss strengths and weaknesses of quasi-experimental designs used in health care quality improvement research. The target groups for this article are investigators in plan-do-study-act (PDSA) quality improvement initiatives who wish to improve the rigor of their methodology and publish their work and reviewers who evaluate the quality of research proposals or published work.
Summary: A primary purpose of PDSA quality improvement research is to establish a functional relationship between process changes in systems of health care and variation in outcomes. The time series design is the fundamental paradigm for demonstrating such functional relationships. The rigor of a PDSA quality improvement study design is strengthened using replication schemes and research methodology to address extraneous factors that weaken validity of observational studies.
Conclusion: The design of PDSA quality improvement research should follow from the purpose and context of the project. Improving the rigor of the quality improvement literature will build a stronger foundation and more convincing justification for the study and practice of quality improvement in health care.