Chapter 14: Q1CQQ (page 654)
What are process data?
Process data represents the measurement of a variable/characteristic/feature of goods/services that are produced involving equipment, people, material, procedures, and circumstances. It is often measured on a time scale.
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Control Charts for p. In Exercises 5–12, use the given process data to construct a control chart for p. In each case, use the three out-of-control criteria listed near the beginning of this section and determine whether the process is within statistical control. If it is not, identify which of the three out-of-control criteria apply
Car Batteries Defective car batteries are a nuisance because they can strand and inconvenience drivers, and drivers could be put in danger. A car battery is considered to be defective if it fails before its warranty expires. Defects are identified when the batteries are returned under the warranty program. The Powerco Battery corporation manufactures car batteries in batches of 250, and the numbers of defects are listed below for each of 12 consecutive batches. Does the manufacturing process require correction?
3 4 2 5 3 6 8 9 12 14 17 20
Defective Child Restraint Systems The Tracolyte Manufacturing Company produces plastic frames used for child booster seats in cars. During each week of production, 120 frames are selected and tested for conformance to all regulations by the Department of Transportation. Frames are considered defective if they do not meet all requirements. Listed below are the numbers of defective frames among the 120 that are tested each week. Use a control chart for p to verify that the process is within statistical control. If it is not in control, explain why it is not.
3 2 4 6 5 9 7 10 12 15
Control Charts for p. In Exercises 5–12, use the given process data to construct a control chart for p. In each case, use the three out-of-control criteria listed near the beginning of this section and determine whether the process is within statistical control. If it is not, identify which of the three out-of-control criteria apply
Euro Coins Repeat Exercise 5, assuming that the size of each batch is 100 instead of 10,000. Compare the control chart to the one found for Exercise 5. Comment on the general quality of the manufacturing process described in Exercise 5 compared to the manufacturing process described in this exercise.
Energy Consumption. Exercises 1–5 refer to the amounts of energy consumed in the author’s home. (Most of the data are real, but some are fabricated.) Each value represents energy consumed (kWh) in a two-month period. Let each subgroup consist of the six amounts within the same year. Data are available for download at www.TriolaStats.com.
Jan.-Feb. | Mar.-April | May-June | July-Aug. | Sept.-Oct. | Nov.-dec. | |
Year 1 | 3637 | 2888 | 2359 | 3704 | 3432 | 2446 |
Year 2 | 4463 | 2482 | 2762 | 2288 | 2423 | 2483 |
Year 3 | 3375 | 2661 | 2073 | 2579 | 2858 | 2296 |
Year 4 | 2812 | 2433 | 2266 | 3128 | 3286 | 2749 |
Year 5 | 3427 | 578 | 3792 | 3348 | 2937 | 2774 |
Year 6 | 4016 | 3458 | 3395 | 4249 | 4003 | 3118 |
Year 7 | 4016 | 3458 | 3395 | 4249 | 4003 | 3118 |
Year 8 | 4016 | 3458 | 3395 | 4249 | 4003 | 3118 |
Energy Consumption:\(\bar x\)Chart Let each subgroup consist of the 6 values within a year. Construct an\(\bar x\)chart and determine whether the process mean is within statistical control. If it is not, identify which of the three out-of-control criteria lead to rejection of a statistically stable mean.
Notation The control chart for Exercise 1 shows a value of \(\bar p\) = 0.0975. What does that value denote, and how is it obtained? What do UCL and LCL indicate?
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