This document specifies the methodology for the design, planning, and execution of an interlaboratory study (ILS) and calculation of precision estimates of a test method specified by the study. In particular:

• it defines the relevant statistical terms,
• it specifies the procedures to be adopted in the planning and execution of an ILS to determine the precision of a test method, and
• it specifies the method of calculating the precision from the results of such a study.

The procedures in this document have been designed specifically for petroleum and petroleum related products, which are normally considered as homogeneous. However, the procedures described in this document can also be applied to other types of homogeneous products.