D_Statistical_Process_Control

D_Statistical_Process_Control - Reading Pages 109 2nd...

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BIT 3414 Copyright 2011 p. 1 Statistical Process Control Walter Shewhart developed the foundations of Statistical Process Control working with Bell Telephone Labs in the 1920s. SPC monitors a production process to detect and prevent poor quality Periodically take a sample from a process Calculate a statistic of interest from the sample Plot the statistic on a control chart Determine if the process is in control Prevent quality problems Process Control Chart Signs of a process in control No sample points outside limits Most points near process average About equal number of points above and below centerline Points appear randomly distributed Reading Pages 109 – 2 nd paragraph 119 middle 120 – 2 nd paragraph 125 middle 127 – top 132 1 2 3 4 5 6 7 8 9 10 Sample Process average
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BIT 3414 Copyright 2011 p. 2 The Normal Distribution Types of Variation Observed Assess the chart to determine if the variation present is inherent to the process or if it needs to be removed Common Causes of Variation ever-present factors that contribute to small, random shifts in output difficult to track to a source Special Causes of Variation identifiable factors that induce variation beyond the inherent variation in the system can usually be tracked to a source =0 1 2 3 -1 -2 -3
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BIT 3414 Copyright 2011 p. 3 Initial Construction of a Control Chart Decide what to measure or count Attribute Data product characteristic evaluated with a discrete choice Variable Data product characteristic that can be measured on a continuous scale Collect the sample data
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D_Statistical_Process_Control - Reading Pages 109 2nd...

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