This Technical Report provides guidance to scientists, engineers and technicians, working in the field of rubber materials and products, to supplement ISO/IEC Guide 98-3 and to provide additional guidance in situations where functional relationships between input quantities (such as temperature, strain rate and time) and derived output quantities (such as tensile strength and compression set) are unknown and where no other guidance is available. This Technical Report provides a summary of the classical approach that is taken in the preparation of uncertainty budgets and provides in Clause 4 a list of selected test methods and, for each, an indication of the factors that will make a contribution to the uncertainty budget. Clause 5 discusses how “non-functional” factors can be taken into account in the classical approach.