Abstract: Repeatability and reproducibility estimates of standard analysis were used to determine the uncertainty for lead content in copper, lead and zinc ores, by the EDTA volumetric method. Excesses in laboratory bias and repeatability were examined by 7 different laboratories collaborating for this experiment. It was determined that the measurement uncertainty relates to the accuracy of reproducibility when bias and precision are the dominant factors. This method proved to be efficient and effective by employing standards in collaboration experiments.