Parametric and non-parametric prediction intervals based phase II control charts for repeated bioassay data

Quality control for repeated bioassay runs can be performed by phase H control charts, well-known from industrial quality control. The value of interest is the potency, of which a single value per run is available. Parametric and non-parametric prediction intervals are described to estimate quality control intervals for future re-test runs. Violations against the normal distribution occur in real data frequently, particularly outliers. The non-parametric prediction intervals are limited to not too small sample sizes in both the historical and future sampling phases. Therefore, robust prediction intervals based on winsorization are proposed. R-functions for all prediction intervals are provided. (C) 2009 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.