Statistical Treatment, Reports, and Supporting Documents

Information is provided here on the statistical approach employed in the Magruder Fertilizer Check Sample program.

  Statistical procedures and approaches

   Here is a pdf presentation in slide form describing the calculations and parameters used to summarize the information from a sample dataset and the International Harmonized Protocol which statistical treatment of the data is based.

  AAFCO Reports Magruder Proficiency Testing Program Statistics Documentation.
  AAFCO Reports The International Harmonized Protocol For The Proficiency Testing Of Analytical Chemistry Laboratories (IHP, 2006).

Examples of Reports

Here are examples of Report Cards and the Master Lists for all the data derived from a single sample.

AAFCO Reports Example of a Proficiency Test Report Card for a Lab.
AAFCO Reports Example of an Individual Method Proficiency Test Report Card for a Lab.
AAFCO Reports Example of Analyte All Tests Report
AAFCO Reports Example of Method All Tests Report
AAFCO Reports Example of Analyte Statistical Summary
AAFCO Reports Example of Individual Method Performance Summary.

Sample Homogeneity and Stability Evaluation

Here are presentations on sample homogeneity and stability monitoring. Of particular interest is a pseudo homogeneity/stability check we have established for every sample.

AAFCO Reports Homogeneity Monitoring.
AAFCO Reports Stability Monitoring.

Documents published by The Analytical Methods Committee of The Royal Society of Chemistry

Here are selected short supporting documents. There is a great deal of literature describing the applications of Robust Statistics over an extremely diverse range of subjects. John Tukey, Peter Huber and Frank Hampel have been credited with founding the discipline and all this since the landmark paper by Tukey in 1960. So, you can see that this is a fairly young science nevertheless, the literature and bookshelves are rife with the subject.

AAFCO Reports Analytical Methods Committee 2 page Technical Brief describing the Robust Calculations used in the IHP and ISO 13528.
AAFCO Reports Analytical Methods Committee 2 page Technical Brief on representing data distributions with kernel density estimates.
AAFCO Reports Analytical Methods Committee 2 page Technical Brief describing and using the "Fitness for Purpose" criterion.
AAFCO Reports Analytical Methods Committee 2 page Background Paper "What is proficiency testing?"
AAFCO Reports Analytical Methods Committee 2 page Technical Brief describing Creating your own ffp criteria.
AAFCO Reports Analytical Methods Committee 5 page report on "Robust Statistics - How Not to Reject Outliers", 1989
AAFCO Reports Analytical Methods Committee 2 page Technical Brief on "The amazing Horwitz function"

Interesting Articles

AAFCO Reports Short 3 page philosophical description of Robust Statistics by Frank Hampel (2001).
AAFCO Reports Short 3 page description of the historical development of Robust Statistics by Elvezio Ronchetti (2006).

Pertinent references to which open access can not be provided

"Robust Estimation and Hypothesis Testing", 2nd Ed., Rand R. Wilcox, 2005, Elsevier

"Robust Statistics", 2nd Ed., P.J. Huber and E.M. Ronchetti, 2009, Wiley

"Robust Statistics: The Approach Based on Influence Functions", F.R. Hampel, E.M. Ronchetti, P.J. Rousseeuw and W.A. Stahel, 1986, Wiley

"A survey of sampling from contaminated distributions", J.W. Tukey, (1960). In "Contributions to Probability and Statistics.", I. Olkin, S.G. Ghurye, W. Hoeffding, W.G. Madow and H.B. Mann (Eds), Stanford University Press, pp. 448485.