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Exam 16: Quality Control and Spc

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Question 21

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c-charts

A) Are used for the fraction of non-conforming items
B) Count the number of nonconformances per unit
C) Use continuous metrics
D) Can have negative lower limits

E) A) and B)
F) A) and C)

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Question 22

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Define "quality at the source."

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Quality at the source means that the peo...

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Question 23

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The center line p-bar) for a p-chart is 0.50 with an UCL = 0.70 and a LCL = 0.35. The results of the next eight sample means are 0.45, 0.60, 0.39, 0.44, 0.48, 0.53, 0.54, and 0.61. What would you do?

A steel company is interested in determining if a particular process in its mini?mill is capable of meeting customer expectations. The thickness of steel has an upper limit of .540 mm and a lower limit of .480 mm. The process has a standard deviation of .02 mm. a. What is the process capability index (C_p) for this process? b. What must the standard deviation of the process be changed to for the C_p to equal 1.00?

Which of the following is most closely related to Statistical Process Control (SPC) ?

In developing process control charts, if special causes are present, they are not representative of true state of statistical control, and the calculations of the center line and control limits will be biased.

Jim is a quality control manager at a clothing manufacturer. He is studying a quality problem where zippers are purchased from an outside supplier and have been discovered to be poorly constructed. When the zipper is manufactured correctly, it should have a mean length of 15 inches and a range of .5 inches. Jamie proposes that 25 samples of five observations each should be collected on a daily basis. He plans to prepare control charts to monitor the progress of the supplier's quality performance on the zippers. a. What are the upper and lower control limits and center line for an R chart? b. What are the upper and lower control limits and center line for an X?bar chart?

In general, discuss how to interpret control charts.

To account for the process centering, a two-sided capability index is often used.

p-charts

Find the control limits for a c chart with $\bar { C }$ = 7.

In manufacturing, quality control is generally applied at the receiving stage from suppliers, during various production processes, and at the finished goods stage.

A process is considered to be in control when all common and special causes have been eliminated.

Quality at the source means that quality is controlled by

As long as no points are outside of the control limits in a control chart, the process would be considered to be in control

Which one of the following statements is true?

A supplier is producing a machined part for the transmission of your vehicle. The upper specification limit is 0.125 cm and the lower specification limit is 0.085. The process standard deviation for the process that makes this part is 0.008 and the process average is 0.105. What conclusion can be drawn from these process capability data?

A Procter and Gamble factory process fills boxes with detergent. Construct an appropriate set of control charts to monitor the process. Historical data for fill weight in ounces) of eight samples is presented below. A sample size of six was used. $\begin{array} { c c c } \text { Sample } & \text { Sample Mean } & \text { Sample Range } \\\hline1 & 15.80 & 0.42 \\ 2 & 16.10 & 0.38 \\ 3 & 16.02 & 0.08 \\ 4 & 15.95 & 0.15 \\ 5 & 16.12 & 0.42 \\6 & 16.18 & 0.23 \\ 7 & 15.87 & 0.36 \\ 8 & 16.20 & 0.40 \\\end{array}$ a.Compute the limits for both an R chart and x-bar chart. Compare the sample results to the limits of the charts. b.Briefly explain what the quality control charts tell you. What actions, if any, would you take?

Describe the steps required to develop and use control charts.

The lower the rate of defects, the higher the sample size should be in p-charts.