This document provides guidance for carrying out round robin tests (RRT) and hence for the determination of levels of repeatability (intra-laboratory variability) and reproducibility (interlaboratory variability) for household and similar electrical appliances. This document can also be used to verify the measurement methods@ to improve the measurement method@ and to qualify laboratories. It is not applicable for the determination of production variation for a particular product. General advice on proficiency testing of laboratories is given in ISO/IEC 17043. This document can be used in addition to ISO/IEC 17043. NOTE The repeatability and reproducibility levels are important factors for the establishment of uncertainty margins of the measurement methods and for the definition of tolerance levels in verification schemes.