Determining the concentration of microorganisms controlled by attributes sampling plans

We present a method of translating the performance of attributes sampling p lans, such as those recommended by the International Commission on Microbio logical Specifications for Foods (ICMSF), so that the user can estimate the concentration of organisms that any plan may control. The method is based on the assumption that sampling results for organisms in foods are log-norm ally distributed. The normal distribution of log counts is used to estimate the proportion of defective (and marginally acceptable) material for a pop ulation of known (or, more usually. estimated) mean and standard deviation and then to determine the probability of acceptance. The method is presente d in the form of a spreadsheet and is fully described and illustrated with examples of the performance of ICMSF plans in terms of concentrations of or ganisms controlled. The use of this approach to validate the use of samplin g plans to meet a given performance criterion towards meeting a Food Safety Objective is also discussed. (C) 2001 Elsevier Science Ltd. All rights res erved.