System verification and validation are performed to secure that a system fulfils the different quality aspects, such as reliability, functionality, maintainability, performance and user friendliness. Since the verification and validation activities take a large share of the total project budget, efficiency and effectiveness are key issues. In this paper a method is presented for application of the well-known technique for experimental planning, factorial design, to validation of system performance. The proposed method is applied in this case study to the validation of the effectiveness of a radar system. It is concluded that the factorial design is a considerable support for the validation planning, enabling efficient system performance validation. The cost reduction was in this case 40%, compared with the previously used method. At the same time more information of the effects of factors was gained.