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IEOR 165 Lecture 14 June 24 2009

IEOR 165 Lecture 14 June 24 2009 - Quality Control Ratings...

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Quality Control Ratings are mostly based on the quality of, for instance, cars. Lemming, a statistician, proposed Quality Control and in the 60s, there wasn’t really a concern for quality in the US. People were more concerned with the look/comfort. The Japanese took into high consideration, Lemming’s ideas. (1) First step: Characterize the variability. (Test & discover the level of variation) (2) Second step: Define Acceptable variability/specification UPL LPL (upper/lower process limit) USL LSL (upper/lower specification limit) N(mean, variance) measurement Target mean μ0 LSL μ μ0 USL (3) Step 3: Center the process to the target If the difference between LSL and USL is large, then my customer doesn’t care what he/she gets and we don’t need to care about quality. But if the difference is small, then we need to spend more time with quality control. Process capability: = - cp USL LSL6σ If the process is centered, the Cp (process capability) immediately reveals their defectives per million items produced (Dpm)
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LSL= - μ 3σ USL= + μ 3σ = μ μ0
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