Statistical Aspects of the Microbiological Examination of Foods


  • Basil Jarvis, Department of Food and Nutritional Sciences, School of Chemistry, Food and Pharmacy, The University of Reading, READING, RG6 6AP, UK
  • Basil Jarvis, Department of Food and Nutritional Sciences, School of Chemistry, Food and Pharmacy, The University of Reading, READING, RG6 6AP, UK

For many biologists, statistics are an anathema; but statistical analysis of quantitative and qualitative data is of considerable importance. Although spreadsheet software provides a diverse range of statistical tools, users are usually unsure which technique should be used. This book provides the basic statistical theory and practice to understand the types of tests frequently needed for the assessment of microbiological data. No prior knowledge of statistical techniques is required. Even when data can be given to a professional statistician for analysis, the microbiologist needs to have at least a general understanding of the underlying basis of statistical procedures in order to communicate effectively with the statistician. The book contains many worked examples to illustrate the use of the techniques and provides a plethora of references both to standard statistical works and to relevant original scientific papers on food microbiology.
View full description


Microbiologists, food microbiologists, applied microbiologists, food scientists, food technologists, official analysts, environmental health officers.


Book information

  • Published: July 2008
  • ISBN: 978-0-444-53039-4

Table of Contents

1 Introduction2 Some Basic Statistical ConceptsPopulationsLots and SamplesAverage Sample PopulationsStatistics and ParametersVariance and Error References 3 Frequency DistributionsIntroductionTypes of frequency distributionStatistical probabilityThe Binomial distributionThe Normal distributionThe Poisson DistributionThe Negative Binomial DistributionRelationship between the frequency distributionsTransformations References 4 The distribution of microorganisms in foods in relation to samplingRandom distributionRegular distributionContagious (heterogeneous) distributionsEffects of sample size References 5 Statistical Aspects Of Sampling For Microbiological Analysis Attributes and Variables SamplingBinomial and trinomial distributionsAccuracy of the sample estimateAcceptance sampling by attributesAcceptance sampling by variablesStatistical considerations about drawing representative samplesReferences 6 Errors In The Preparation Of Laboratory Samples For AnalysisLaboratory sampling errorsDiluent volume errorsPipette volume errorsOther sources of errorCalculation of the relative dilution error References 7 Errors Associated With Colony Count ProceduresSpecific technical errorsPipetting and distribution errorsLimiting precision and confidence limits of the colony countGeneral technical errors Comparability of colony count methodsOverall error of colony count methods References 8 Errors Associated With Quantal Response MethodsDilution Series and Most Probable Number countsMultiple Test Dilution SeriesQuantification based on relative prevalence of defectivesSome statistical aspects of multi-stage testsReferences 9 Statistical Considerations Of Other Methods In Quantitative MicrobiologyDirect microscopic methodsIndirect methods References 10 Measurement Uncertainty in Microbiological AnalysisAccuracy and PrecisionMeasurement Uncertainty How is uncertainty estimated?Reporting of uncertaintySampling uncertaintyThe use of uncertainty measures in assessing compliance References 11 Estimation Of Measurement UncertaintyThe ‘Generalised Uncertainty Method’ (GUM) or bottom-up procedureThe Top-down Approach to Estimation of UncertaintyAnalysis of VarianceRobust Methods of Analysis of Variance (ANOVA)Measurement of Intermediate ReproducibilityEstimation of Uncertainty Associated with Quantal Methods References 12 Statistical Process Control using Microbiological DataWhat is Statistical Process Control?Trend analysisTools for Statistical Process ControlShewart’s Control Charts for Variables DataCUSUM ChartsControl Charts for Attribute DataConclusion References 13 Validation of Microbiological Methods (Dr Sharon Brunelle, AOAC International, Woodville, WA, USA)The Stages of Method Development What is Validation?Statistical Methodologies in Method ValidationMethod Comparison – Qualitative MethodsStatistical Analysis of Paired Sample Design - Single Laboratory and Collaborative Laboratory Validation Statistical Analysis of Unpaired Sample Design - Single Laboratory and Collaborative Laboratory Validation Method Comparison – Quantitative Methods- Single Laboratory and Collaborative Laboratory StudiesExamination of Data for Outliers Future Directions References 14 Statistical aspects of microbiological criteria for foods in relation to Food Safety ObjectivesFood Safety Objectives and Risk AssessmentMicrobiological CriteriaThe relevance of microbial measurement uncertainty to microbiological criteriaConclusions