This article discusses Quantum, an instructor-mediated performance assessment test, used in simulation to assist nurse educators to objectively measure student performance and document clinical competency. The article describes the process of development, validation, and measurement of student’s integrated knowledge, skills, attitudes, and clinical reasoning used in decision-making to improve safe effective nursing practice. The article provides a review of Quantum’s evaluation framework including: patient safety, assessment, communication, intervention, and documentation. The sample comprised of pre-licensure student nurses enrolled in core nursing courses from 14 nursing programs. Classical and Rasch data analyses found empirical evidence in support of the reliability of measures and validity of inferences in terms of content validity, optimum scoring structure, unidimensionality, reliability, invariance, responsiveness, consequential validity, and interpretability