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Defect Levels in the Incoming Process Distribution

IP.com Disclosure Number: IPCOM000082983D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Kulkarni, MV: AUTHOR [+4]

Abstract

In many industrial situations where an accept/reject decision is to be taken on the lots submitted for inspection, the process history is not used. Consequently, the true process average and the defect levels from batch-to-batch or lot-to-lot go undetected.

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Defect Levels in the Incoming Process Distribution

In many industrial situations where an accept/reject decision is to be taken on the lots submitted for inspection, the process history is not used. Consequently, the true process average and the defect levels from batch-to- batch or lot-to-lot go undetected.

Using prior information on the parameters of the process (or its past history), a program is described which will not only provide the plot of the process distribution, but will give the incoming process average and will produce a table indicating a breakdown on the percentage of lots exceeding specified percentage defectives. This will eliminate the sampling inspection, if the process is already meeting the stipulated requirements on either the outgoing average defect level or a certain percentage of lots not exceeding the desired defect level in the shipped product.

A conversational APL program (see flow chart) uses as an input, a vector of sample sizes and a corresponding vector of defects in these samples. For a Beta distributed process, the parameters are then estimated from the input data. The output of the program consists of the following: a) Number of samples, process parameters, incoming average defect levels; b) Plot of the process distribution; and, c) Table of percent of lots exceeding specified percentage defectives.

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