Improving the Validity of Causal Inferences in Observational Studies

Editor's note: This is the 13th article in a series on clinical research by nurses. The series is designed to be used as a resource for nurses to understand the concepts and principles essential to research. Each column will present the concepts that underpin evidence-based practice—from research design to data interpretation. To see all the articles in the series, go to https://links.lww.com/AJN/A204.