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Multiattribute acceptance sampling plans - Library(ISI Kolkata ...

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Part 0 : Introduction<br />

0.1 Purpose of <strong>sampling</strong> inspection<br />

The very purpose of quality management comprising of quality planning, quality control,<br />

quality assurance and quality improvement is to achieve simultaneously, improvement in<br />

customer satisfaction, improvement in productivity and reduction in costs of product at all<br />

stages. From the very beginning statistical methods have been developed, established and<br />

implemented as support activities for the above purpose. While Shewhart (1931) focused his<br />

attention on economic control of quality of manufactured product, Dodge and Romig (1929)<br />

attended to quality assurance activities of an organization for protection of the interest of<br />

the internal and external customers at reduced cost of inspection and cost of production,<br />

and also for attainment of uniform quality. The latter established methodologies of <strong>sampling</strong><br />

inspection for separating lots or batches of mass produced items into lots of satisfactory and<br />

unsatisfactory quality.<br />

0.2 Theory and application of <strong>sampling</strong> inspection - a short review<br />

In the following sections we try to underline the nature of major developments of techniques<br />

of <strong>sampling</strong> inspection for industrial quality assurance since the pre-war time. In this context<br />

we limit our discussions at the beginning to single <strong>sampling</strong> <strong>plans</strong> as employed for lot-by-lot<br />

inspection by attribute. The developments relating to double and multiple <strong>sampling</strong> <strong>plans</strong><br />

for attributes, continuous <strong>sampling</strong> and chain <strong>sampling</strong> <strong>plans</strong>, sequential <strong>sampling</strong> <strong>plans</strong> and<br />

their modification and the whole subject matter of <strong>sampling</strong> <strong>plans</strong> by variables and all methods<br />

pertaining to bulk materials are scrupulously excluded from our discussions as they are<br />

not relevant as far as the scope of the present thesis is concerned. The historical perspective<br />

discussed focuses attention only to that part of the development which is conceptually and<br />

theoretically related to the problems studied in the present thesis. A single <strong>sampling</strong> plan<br />

is defined by means of three parameters c, n, and N and the following rule : From each lot<br />

of size N take a random sample of size n. If the number of defectives in the sample is less<br />

than or equal to the <strong>acceptance</strong> number c, accept the lot, otherwise reject the lot.<br />

2

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