Extended and comprehensive evaluation model based on some sample units and its properties

First we present an extended and comprehensive evaluation model based on some sample units (SDEA) in this paper. Second we discuss the influence on efficiency of observed Decision Making Units (DMUs) when the number of the sample units and the number of their input indexes and output indexes are changed. At the same time we show that sufficient or necessary condition to the change of efficiency. This will be conducive to determining the efficiency of DMUs. Moreover original model can be extended further when the model has negative outputs.