On the Use of the Horwitz Ratio (HorRat) As an Acceptance Criterion for Dietary Fiber Collaborative Studies

The quest for optimum methodology for any analyte often includes a study of the method in multiple independent laboratories. Evaluation of the results of these studies is typically subjective; however, various attempts have been made to increase the objectivity of the evaluation. Among the objective propositions is the use of the Horwitz Ratio (HorRat) as applied to collaborative study statistics. A historical review of fiber method validation studies performed since 1940 shows that the Horwitz curve does not effectively predict the results of dietary fiber collaborative studies, either retrospectively or prospectively. Consequently, use of the HorRat as a criterion for accepting or rejecting dietary fiber methods is contraindicated. An alternative, objective statistical approach is proposed that may also apply to collaborative studies of other empirical analytical methods in general.