DOD system testing spans multiple phases of developmental, integrated, and operational testing which results in multiple data sources for assessing system performance. Additionally, multiple methods of testing may be employed in each phase of testing including such approaches as modeling and simulation, hardware in the loop, and full system hardware and software tests. These different test phases and test processes produce disparate datasets for which historic methods for analyzing test data are frequently inadequate if one desires to combine information gained across different test events. In the current financial climate, test schedule and test scope restrictions often conflict with the need to provide the best information on system performance to the war fighter and therefore it is prudent to effectively utilize emerging analysis methodologies for combining information across multiple test events. This presentation provides a survey of several historical and contemporary methods for combining and analyzing system test data and discusses the inherent strengths and weaknesses of each method. Sample historical data from DOD systems will be used to illustrate the different methods. In addition, current DOD urgent needs for improved methods of combining test data from disparate sources will be mentioned including, most notably, a need to effectively support Operational Testing performance and reliability system requirements in a limited data environment.