chapter  8
Process control by attributes
Pages 32

The quality of many products and services is dependent upon characteristics which cannot be measured as variables. These are called attributes and may be counted, having been judged simply as either present or absent, conforming or non-conforming, acceptable or defective. Such properties as bubbles of air in a windscreen, the general appearance of a paint surface, accidents, the particles of contamination in a sample of polymer, clerical errors in an invoice and the number of telephone calls are all attribute parameters. It is clearly not possible to use the methods of measurement and control designed for variables when addressing the problem of attributes.