Submitted to: Cereal Foods World
Publication Type: Trade Journal
Publication Acceptance Date: November 1, 2004
Publication Date: February 4, 2005
Citation: Delwiche, S.R., Palmquist, D.E., Lynch, J. M. 2005. Collaborative Studies for Cereals Analysis. Cereal Foods World. 50:9-17.
Interpretive Summary: Professional organizations, such as the American Association of Cereal Chemists (AACC), frequently deal with the development of analytical methods that are used for quantitative analysis of a constituent or property. Perhaps even more important than the accuracy of the method itself is the ability for the method to produce the same values when evaluated in either the same laboratory on different days or in other laboratories. Collectively known as the 'precision' of a method, these figures of merit are necessary components in order for the method to become sanctioned or 'approved' by the organization. This paper describes a set of international guidelines that have been adopted by the AACC that govern the design and analysis of what is known as a collaborative, or interlaboratory study, which is used to evaluate the precision of an analytical method. Aspects of numbers of participating laboratories, numbers of materials, outlier testing, and statistical procedures for determination of 'repeatability' (within laboratory precision) and 'reproducibility' (among laboratory precision) are introduced and explained. This article is intended for any scientist in cereals or foods analysis who is contemplating the development of a new quantitative procedure for regulation, trade, or quality control.
Collaborative, also known as interlaboratory, studies are frequently performed by analytical chemists as a means to document the precision of quantitative procedures. In the cereals community, this may be a gravimetric, titrimetric, amperometric, or physical procedure to measure the concentration of a naturally occurring component, an ingredient, or the response to a processing condition such as dough mixing or baking. Through application of classical statistical principles, the collaborative study produces information on the level of variability (precision) that can be expected of a procedure when it is performed by one laboratory over a reasonable timeframe (repeatability), as well as when it is performed by multiple laboratories (reproducibility). The Approved Methods Committee of the AACC is the responsible party that oversees the development and approval of new methods for the Association. This article is devoted to the design and analysis of collaborative studies, particularly from a statistics standpoint. Issues of required numbers of materials, blind replicates, matched-pairs, statistical tests for outliers, and analyses of variance (ANOVA) are discussed. Theory and application (spreadsheet programs and ANOVA tables) are mutually considered.