Validity of the Percent Reduction in Standard Deviation Outlier Test for Screening Laboratory Means from a Collaborative Study
Abstract:AOAC INTERNATIONAL recommends an outlier test that is based on the “percent reduction in standard deviation” (PRSD) for screening the highest or lowest and 2-highest or 2-lowest laboratory means from a collaborative study. The original critical values that were developed to assess the significance of the test statistics associated with the PRSD test were obtained by simulation. In this paper, we answer several questions relative to the validity of the simulated critical values and develop formulas, based on the Student's t-distribution, to compare the simulated and formula-based critical values. Assumptions and derivations of formulas are provided along with selected tabular critical values that are used to test hypotheses at various levels of significance.
Document Type: Research Article
Affiliations: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Scientific Analysis and Support, Division of Mathematics, 5100 Paint Branch Pkwy, College Park, MD 20740-3835
Publication date: September 1, 2003
- The Journal of AOAC INTERNATIONAL publishes refereed papers and reviews in the fields of chemical, biological and toxicological analytical chemistry for the purpose of showcasing the most precise, accurate and sensitive methods for analysis of foods, food additives, supplements and contaminants, cosmetics, drugs, toxins, hazardous substances, pesticides, feeds, fertilizers and the environment available at that point in time. The scope of the Journal includes unpublished original research describing new analytical methods, techniques and applications; improved approaches to sampling, both in the field and the laboratory; better methods of preparing samples for analysis; collaborative studies substantiating the performance of a given method; statistical techniques for evaluating data. The Journal will also publish other articles of general interest to its audience, e.g., technical communications; cautionary notes; comments on techniques, apparatus, and reagents.
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