Chapter 09 Quality Control and Improvement Chapter 9 Quality Control and Improvement Answer Key Multiple Choice Questions 1 A complete system of quality control A is defined by critical control points inspectors measurements costs and other considerations B involves a zero defects philosophy C requires a continuous scale for measurement of defects D must include both variable and attribute measurements LO 9 1 Topic Design of Quality Control Systems Difficulty 3 Hard AACSB Reflective thinking Bloom s Understand Feedback The steps include identifying critical points deciding type of measurement amount of measurement and who will do the inspection Cost is always a factor 2 Sampling inspection by attributes A means each item sampled is classified as defective or not defective based on quality standards B could be used together with process control and variable measurement as part of a quality control system C utilizes a discrete scale of measurement D a b and c LO 9 2 Topic Process Quality Control Difficulty 2 Moderate AACSB Reflective thinking Bloom s Understand Feedback Attribute measurement uses a discrete scale e g defective or not defective and can be used along with variables measurement in a QC system 3 Which of the following statements about process quality control is NOT true A Assignable cause variation is also referred as special cause variation B An observation outside the control limits is an example of a special cause of variation C Common cause variation can be eliminated from the process by removing the potential causes D The control limits will include 99 74 of the population under the normal probability distribution assuming that the process is in control LO 9 2 Topic Process Quality Control Difficulty 2 Moderate AACSB Reflective thinking Bloom s Understand Feedback No matter how perfectly a process is designed there will be some random variability 9 1 Chapter 09 Quality Control and Improvement 4 A process control chart A assumes that 99 74 of special cause variation will fall between upper and lower limits B has upper and lower control limits set at 2 standard deviations from the center line C separates the assignable cause of variation from the common cause of variation D assigns causes of variation to operator machine or material LO 9 2 Topic Process Quality Control Difficulty 3 Hard AACSB Reflective thinking Bloom s Understand Feedback A control chart assumes that 99 74 of common cause variation will fall between plus minus 3 standard deviations of the mean but the chart does not assign causes It does separate special cause variation from common cause variation 5 A Pareto diagram A shows causes and effects of quality problems B shows the prevalence of the various types of defects that have been found C is not useful when first studying a quality problem D has both upper and lower specification limits LO 9 4 Topic Continuous Improvement Difficulty 2 Moderate AACSB Reflective thinking Bloom s Understand Feedback Pareto diagrams show the more important problems by volume or occurrence prevalence 6 A cause and effect diagram A identifies common causes of quality defects B is often used in conjunction with a Pareto chart C is also called a fishbone diagram D has all of the above features LO 9 4 Topic Continuous Improvement Difficulty 1 Easy AACSB Reflective thinking Bloom s Remember Feedback CE diagrams help identify causes are often used with Pareto analysis to explore causes of the most prevalent problems and are often called fishbone diagrams 7 Which of the following statements about process capability is accurate A Cpk is a better measure of process capability than Cp B Cp is exactly equal to Cpk when the mean is centered in the specification limits C Given the same process Cpk is always less than or equal to Cp D All of the above are accurate LO 9 3 Topic Process Capability 9 2 Chapter 09 Quality Control and Improvement Difficulty 2 Moderate AACSB Reflective thinking Bloom s Understand Feedback All are correct see Section 9 6 8 Suppose that a process is in a state of control and we have the following information for a human weights measurement study Average weight of males in the study 150 lbs Average range of the male weights 100 lbs A2 577 D3 0 D4 2 115 What is the upper control limit for the average mean chart A 207 7 lbs B 92 3 lbs C 361 5 lbs D 175 lbs LO 9 2 Topic Process Quality Control Difficulty 2 Moderate AACSB Application of knowledge Bloom s Apply Feedback Applying the variables UCL formula for the averages chart see Section 9 4 150 577 100 207 7 lbs 9 Using the information from Question 8 what is the upper control limit for the range chart A 57 7 lbs B 211 5 lbs C 317 25 lbs D 86 55 lbs LO 9 2 Topic Process Quality Control Difficulty 2 Moderate AACSB Application of knowledge Bloom s Apply Feedback Applying the variables UCL formula for the range chart see Section 9 4 2 115 100 211 5 lbs 10 Suppose that you have taken 30 samples of 200 units each and calculated the proportion defective as p 075 What is the upper control limit for a p chart A 2192 B 0191 C 1309 D 7500 LO 9 2 Topic Process Quality Control Difficulty 3 Hard AACSB Application of knowledge Bloom s Apply Feedback Applying the attributes UCL formula see Section 9 3 pbar 3 std dev 075 0058 1309 9 3 Chapter 09 Quality Control and Improvement 11 Using the same data as in Question 10 what is the lower control limit for a p chart A 0750 B 0191 C 0000 D 0692 LO 9 2 Topic Process Quality Control Difficulty 2 Moderate AACSB Application of knowledge Bloom s Apply Feedback Applying the attributes LCL formula see Section 9 3 pbar 3 std dev 075 0558 0191 12 Of the four choices below which is the earliest step in designing a quality control system A The amount of inspection to use B Who should do the inspection C The type of measurement to be used D Training workers to perform inspection of their own work LO 9 1 Topic Design of Quality Control Systems Difficulty 2 Moderate AACSB Reflective thinking Bloom s Understand Feedback Type of measurement is step 2 amount is 3 who is 4 and training workers would occur after deciding they will do their own inspection 13 The appearance of a restaurant meal that is not satisfactory is an example of A variable measurement B mean chart C range chart D attribute measurement E none of the above LO 9 2 Topic Process Quality Control Difficulty 2 Moderate AACSB Reflective thinking Bloom s Understand Feedback Satisfactory vs not satisfactory is an example of a discrete