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    Three-Class Attributes Plans in Microbiological Quality Control:
    A Contribution to the Discussion (1995)

    Art
    Zeitschriftenartikel / wissenschaftlicher Beitrag
    Autoren
    Hildebrandt, Goetz (WE 8)
    Böhmer, Leonie
    Dahms, Susanne (WE 16)
    Quelle
    Journal of Food Protection; 58(7) — S. 784–790
    ISSN: 0362-028x
    Sprache
    Englisch
    Kontakt
    Institut für Lebensmittelsicherheit und -hygiene

    Königsweg 69
    14163 Berlin
    Tel.+49 30 838 62550 Fax.+49 30 838 46029
    email:lebensmittelhygiene@vetmed.fu-berlin.de

    Abstract / Zusammenfassung

    In this study, the structure of two- and three-class attributes plans is explained and their decision-making process is illustrated by practical examples. Further, the selectivity of attributes plans is compared to that of variables plans by analyzing the corresponding operating-characteristic (OC) curves. Based on the statistical analysis presented, the following conclusions are drawn: (1) Three-class plans are lacking in clarity, because the decision-making process is influenced in a complex way by the relations between variance within a lot, the distance between m and M, and the choice of the maximum allowable number of defectives (acceptance number, cm, cM). (2) Three-class plans (m,M,cm,cM) tend to have nearly the same slope for the OC-function as two-class plans (m,cm). They show less stringency than analogous variables plans (mean-value plans) with known variance and seem to show no marked difference in stringency compared to analogous variables plans in case the variance has to be estimated. (3) Three-class plans imply the principle of zero tolerance. As a consequence, in a heterogeneous lot one extreme result determines the acceptance or rejection of the whole lot, and the consumer's risk tends to be reduced.