In this paper we use a common set between three subjective tests to build a linear mapping of the results of two tests onto the scale of one test identi ed as the reference test. We present our low-cost approach for the design of the common set and discuss the choice of the reference test. The mapping is then used to merge the outcomes of the three tests and provide an interesting comparison of the impact of coding artifacts, transmission errors and error-concealment in the context of Scalable Video Coding.