15_Variable and Other Plans

15_Variable and Other Plans - Spring 2001 Lecture Notes...

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Spring 2001 Lecture Notes - EMSE 282 - Professor Thomas A. Mazzuchi - 1 VARIABLE AND OTHER SAMPLING PLANS VARIABLE SAMPLING PLANS Merits • Advantages - Same OC Curve can be obtained with smaller sample size. - Variable data provide more information. • Disadvantage - cost/observation greater. - distribution of quality quantity must be known or assumed. - separate plan used for each quality measure. - may lead to a rejection of lots with no defectives. Types • Control of lot or process fraction defective. • Control of lot or process parameter. Assumptions • Quality characteristic is (usually) normally distributed
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Spring 2001 Lecture Notes - EMSE 282 - Professor Thomas A. Mazzuchi - 2 Control of Process Parameters (Usually , ) . 5 • Based on hypothesis testing • Design for process mean, one sided, known 5 - Given X N( , ) specify a lower limit X for X (reject if X X ) µ Î8 . 5 # L L - Given we want to accept batches of quality with probability 1 and . α 1 batches of quality with probability , find n, and X . " 2 L Pr{X X | } Pr{ }   œ œ   L 1 X X / n / n . . . . 5 5 1 1 L È È
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