This document covers statistical methodology for assessing the expected agreement between two test methods that purport to measure the same property of a material, and deciding if a simple linear bias correction can further improve the expected agreement. This document is used for analytical methods which measure quantitative properties of petroleum or petroleum products resulting from a multi-sample-multi-lab study (MSMLS). These types of studies include interlaboratory studies (ILS) meeting the requirements of ISO 4259-1 or equivalent and proficiency testing programs (PTP) meeting the requirements of ISO 4259-3 or equivalent, but is not limited to these data providers as long as the data quality requirements are met. A methodology is presented for establishing the limiting value, designated as the between-method reproducibility. This value is expected to be exceeded with a probability of 5 % under the correct and normal operation of both test methods due to random variation for the difference between two results where each result is obtained by a different operator using different apparatus and each applying one of the two methods X and Y on identical material of the result of the X-method has been appropriately bias-corrected in accordance with this practice. NOTE Further conditions for application of this methodology are given in 5.1 and 5.2.