This Guide presents a practical approach to the application of uncertainty of measurement to conformity assessment activities in the electrotechnical sector . It is specifically conceived for use in IECEE Schemes as well as by testing laboratories engaged in testing electrical products to national safety standards. Clause 4 describes the application of uncertainty of measurements principles. Clause 5 provides guidance on making uncertainty of measurement calculations. Annex A gives some examples relating to uncertainty of measurement calculations for product conformity assessment testing.