Continuous collation of data, measurement and evaluation is needed throughout the change process to inform decisions about what change is needed, to review whether changes are having the desired effect, to determine if the change is sustainable and to understand its potential for spread. Data and measurement are used for learning, to identify variation from quality standards, and to provide assurance of quality and outcomes. Data are triangulated from multiple sources. Outcome measures use both quantitative data and qualitative data from people using and providing services, and actively identify impacts in different parts of the system to where the change is made. Evaluation evolves in respond to emerging issues.