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Webster chemical company produces mastics and

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Webster Chemical Company produces mastics and caulking for the constructionindustry. The product is blended in large mixers and then pumped into tubes andcapped.
6-8Chapter 6: Process Performance and QualityWebster is concerned whether the filling process for tubes of caulking is in statisticalcontrol. The process should be centered on 8 ounces per tube. Several samples ofeight tubes are taken and each tube is weighed in ounces.Assuming that taking only 6 samples is sufficient, is the process in statistical control?Tube NumberSample12345678AvgRange17.988.348.027.948.447.687.818.118.0400.7628.238.127.988.418.318.187.998.068.1600.4337.897.777.918.048.007.897.938.097.9400.3248.248.187.838.057.908.167.978.078.0500.4157.878.137.927.998.107.818.147.887.9800.3368.138.148.118.138.148.128.138.148.1300.03Avgs8.0500.38
Consider dropping sample 6 because of an inoperative scale, causing inaccuratemeasures.What is the conclusion on process variability and process average?Tube NumberSample12345678AvgRange17.988.348.027.948.447.687.818.118.0400.7628.238.127.988.418.318.187.998.068.1600.4337.897.777.918.048.007.897.938.097.9400.3248.248.187.838.057.908.167.978.078.0500.4157.878.137.927.998.107.818.147.887.9800.33Avgs8.0340.45
Chapter 6: Process Performance and Quality6-92.Control charts for attributesTEACHING TIPMention examples from banking and manufacturing. Emphasize that defects can becounted.a.p-chart — population proportion defectiveSampling for ap-chart involves a yes or no decision, based on the binomialdistributionTake a random sample ofnunits.Count the number of defectives.Proportion defective = number of defectives ÷ sample sizePlot sample proportion defective on a chart. If it is outside the range betweenthe upper and lower control limits, search for an assignable cause. If cause isfound do not use these data to determine the control limits.UCLp=p+zσpLCLp=pzσpwhereσp=p1 –p(29nTwo things to note:The lower control limit cannot be negativeWhen the number of defects is less than theLCL, then the system is outof control in a good way.We want to find the assignable cause.Findwhat was unique about this event that caused things to work out so well.UseApplication 6.2:p-Chart for Attributesfor an example of ap-chartproblem. The short answers are:p=0.025;UCLp=0.064;LCLp=0;INCONTROLA sticky scale brings Webster’s attention to whether caulking tubes are beingproperly capped. If a significant proportion of the tubes aren’t being sealed,Webster is placing their customers in a messy situation. Tubes are packaged inlarge boxes of 144. Several boxes are inspected and the following number ofleaking tubes are found:SampleTubesSampleTubesSampleTubes138615525941603310917244112186521261926413520172141Total=72
6-10Chapter 6: Process Performance and QualityCalculate thep

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Term
Spring
Professor
ahmed
Tags
Management, Control Chart, Process capability, LCL, process performance

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