A statistical model to evaluate analyte homogeneity for a material.

An underlying assumption for collaborative studies is that the analyte variation among test samples of the material (i.e., matrix and analyte concentration combination) under study has a negligible influence on the estimates of precision for the method. This assumption is expected to be fulfilled when the material under study is prepared (i.e., thoroughly mixed) such that the analyte is distributed uniformly throughout the matrix. Statistical design and intra-class correlation analysis procedures are proposed to assess the similarity or agreement among analytical results among- and within-containers for single and multiple occasions of use (e.g., collaborative and proficiency studies).