Designing and improving acceptance
sampling plans - a tool

Understand the benefits and limitations of acceptance sampling plans in determining whether a batch of product or raw material is of acceptable quality.

Acceptance sampling plans can be used to help determine whether a batch of product or raw material should be accepted or rejected on the basis of quality. Food microbiologists are often asked to design, comment on or apply acceptance sampling plans with specific regard to the microbiological quality of a batch of material or product. It is important that all involved appreciate the effectiveness or otherwise of an acceptance sampling plan in distinguishing between 'good' and 'bad' batches.

This review, which includes a spreadsheet based tool, was developed by a group of microbiologists and statisticians to help food companies understand and exploit the statistical basis of acceptance sampling. Although aimed at microbiologists, the basic approach will be useful to others in the food industry.

Using colour illustrations, the guide carefully introduces concepts such as 'acceptable quality levels' and 'operating characteristics'. It reinforces these through worked examples and a spreadsheet (provided on disk in Microsoft Excel® format) which provides an interactive tool to explore the effects of changing the acceptance criteria ('operating characteristics') and sampling regime.

Contents

• Introduction
• Acceptance sampling plans
• Batch quality and the acceptable quality level (AQL)
• Probability of acceptance: operating characteristics
• Attribute and measurement data
• Using the spreadsheets
• Examples:
   - Evaluating a sampling plan (attribute data)
   - Improving a sampling plan (attribute data)
   - Evaluating a sampling plan (measurement data)
   - Improving a sampling plan (measurement data)

Note: One free copy of the spreadsheet is provided with each copy of the review. It requires a PC with Excel 97 and assumes proficiency with this package. The spreadsheet cannot be provided in any other package nor in other versions of Excel. CCFRA does not undertake to provide support to users of this spreadsheet and is not able to provide support in the use of Excel. Both the spreadsheet and the guide are protected by copyright law.