Statistical Aspects of the Microbiological Examination of Foods (eBook)

Front Cover 1
Statistical Aspects of the Microbiological Examination of Foods 4
Copyright Page 5
Contents 6
List of Tables 10
List of Figures 13
List of Examples 16
Preface 18
Chapter 1 Introduction 20
Chapter 2 Some Basic Statistical Concepts 22
Populations 22
Lots and Samples 23
Average Sample Populations 24
Statistics and Parameters 25
Variance and Error 25
The Central Limit Theorem 26
References 30
Chapter 3 Frequency Distributions 32
Types of Frequency Distribution 38
Statistical Probability 38
The Binomial Distribution 40
The Normal Distribution 43
The Poisson Distribution 45
The Negative Binomial Distribution 49
Relationship Between the Frequency Distributions 56
Transformations 56
References 62
Chapter 4 The Distribution of Microorganisms in Foods in Relation to Sampling 64
Random Distribution 66
Regular Distribution 75
Contagious (Heterogeneous) Distributions 76
Effects of Sample Size 82
References 87
Chapter 5 Statistical Aspects of Sampling for Microbiological Analysis 90
Attributes and Variables Sampling 91
Binomial and Trinomial Distributions 92
Accuracy of the Sample Estimate 96
Acceptance Sampling by Attributes 101
Acceptance Sampling by Variables 112
References 119
Chapter 6 Errors in the Preparation of Laboratory Samples for Analysis 122
Laboratory Sampling Errors 122
Diluent Volume Errors 123
Pipette Volume Errors 124
Other Sources of Error 128
Calculation of the Relative Dilution Error 129
Effects of Gross Dilution Series Errors on the Derived Colony Count 138
References 138
Chapter 7 Errors Associated with Colony Count Procedures 140
Specific Technical Errors 140
Pipetting and Distribution Errors 143
Limiting Precision and Confidence Limits of the Colony Count 147
General Technical Errors 154
Comparability of Colony Count Methods 156
Overall Error of Colony Count Methods 157
References 160
Chapter 8 Errors Associated with Quantal Response Methods 162
Dilution Series and Most Probable Number counts 162
Multiple Test Dilution Series 167
Quantification Based on Relative Prevalence of Defectives 181
Some Statistical Aspects of Multi-stage Tests 184
References 194
Chapter 9 Statistical Considerations of Other Methods in Quantitative Microbiology 196
Direct Microscopic Methods 196
Indirect Methods 199
References 203
Chapter 10 Measurement Uncertainty in Microbiological Analysis 204
Accuracy and Precision 205
Measurement Uncertainty 206
How is Uncertainty Estimated? 207
Reporting of Uncertainty 209
Sampling Uncertainty 209
The Use of Uncertainty Measures in Assessing Compliance 210
References 210
Chapter 11 Estimation of Measurement Uncertainty 214
The 'Generalized Uncertainty Method' (GUM) or Bottom-Up Procedure 214
The Top-Down Approach to Estimation of Uncertainty 217
Analysis of Variance (ANOVA) 217
Robust methods of ANOVA 227
Measurement of Intermediate Reproducibility 234
Estimation of Uncertainty Associated with Quantal Methods 236
References 241
Chapter 12 Statistical Process Control (SPC) using Microbiological Data 244
What is SPC? 244
Trend Analysis 245
Tools for SPC 246
Setting Control Limits 248
Shewhart's Control Charts for Variables Data 249
Conclusion 277
References 277
Chapter 13 Validation of Microbiological Methods For Food 278
The Stages of Method Development 279
What is Validation? 280
Future Directions 292
References 295
Chapter 14 Risk Assessment, Food Safety Objectives and Microbiological Criteria for Foods 298
Food Safety Objectives and Risk Assessment 299
Microbiological Criteria 304
The Relevance of Microbial Measurement Uncertainty to Microbiological Criteria 311
Conclusion 316
References 316
Index 320
A 320
B 320
C 320
D 321
E 321
F 321
G 322
H 322
I 322
K 322
L 322
M 322
N 323
O 323
P 323
Q 323
R 324
S 324
T 325
U 325
V 325
W 325
X 325