This issue of IDA Research Notes showcases IDA’s response to that challenge, centered on the Design of Experiments (DOE) methods championed by the Director, Operational Test and Evaluation in the Department of Defense (DoD), for whom much of our work was undertaken. DOE methods provide structured, efficient, and scientific approaches to test planning. They provide objective methods for assessing test adequacy not only by providing a quantitative basis for assessing how much testing is enough, but also by identifying where in the operational space the test points should be placed. DOE methods also provide an analytical trade-space between test resources and risk, ensuring that tests are adequate to answer important questions. IDA has developed case studies, training materials, and publications that have been instrumental in shaping the T&E community’s approach to applying DOE to operational testing.