This part of ISO 14461?IDF 169 describes a procedure for testing the performance of the colony-count technique within a laboratory by establishing the within-laboratory variability of its technique and identifying those steps that are associated with excessive variability. The procedure is also suitable for checking the proper observance of Good Laboratory Practice (GLP), which may be a prerequisite for participation in interlaboratory tests of colony-count methods. EXAMPLE Appropriate test samples are raw milk, pasteurized milk and dried milk.