The verification effectiveness can be improved with a proper knowledge management, collecting and analyzing data coming from the AIV activities and flight operations of former projects. The ESA Model And Test Effectiveness Database (MAT€D) can be used for this purpose, collecting such data and providing associated statistical analyses to derive feedback for the improvement of the Model and Test Philosophies of future projects. This paper presents a methodology to support analysis of MAT€D data, with the purpose of comparing verification processes of different projects, with a specific emphasis on the environmental tests effectiveness. The used approaches are compared with those reported for each stage and level in ECSS-E-ST-10-03 (Testing). Performed AIV activities, related conditions (e.g. duration, levels) at different stages are considered to build a complexity index framework, and related normalization and aggregation functions are discussed. The related "Test Depth Index" (TDI) is proposed as an innovative method to calculate the completeness of the testing activity in relation to the ECSS standards, as a formal complement to the index currently used in MAT€D, namely MATEI (Model And Test Effectiveness Index). The application to a subset of MAT€D data is presented and recommendations are provided for further improvements
