Exam 13: Statistical Quality Control

You are going to develop an R-chart based on range statistics, and you are using a sample size of 15 for your charting purposes. Which of the following is the upper control limit D₄ factor for the chart?

Statistical process control involves testing random samples of output from a process to determine whether the process is producing items within a preselected range.

The probability associated with rejecting a high-quality lot is denoted in acceptance sampling with the Greek letter alpha.

The capability index (Cpk) calculates the percentage of items being produced within specifications.

In acceptance sampling, the value for the acceptance number (c) is determined by the interaction of the acceptable quality level (AQL), the lot tolerance percent defective (LTPD), the probability of rejecting a high-quality lot (alpha), and the probability of accepting a low-quality lot (beta).

You want to determine the control lines for a p-chart for quality control purposes. If the total number of defects from all samples is 2,500, the number of samples is 100, and the sample size is 500, which of the following would be the standard deviation used in developing the control lines?

The Greek letter alpha is associated with consumer's risk.

You have just used the capability index (Cpk) formulas to compute the two values "min [1, 1]." Which of the following is the proper interpretation of these numbers?

If there are 12 total defects from 10 samples, each sample consisting of 100 individual items in a production process, which of the following is the fraction defective that can be used in a p-chart for quality control purposes?

Total, 100 percent inspection can never be cost justified.

You want to develop a three-sigma R-chart. You know the average range is 12 based on several samples of size 6. Which of the following is the resulting LCL?

You want to determine the lower control line for a p-chart for quality control purposes. You take several samples of a size of 50 items in your production process. From the samples, you determine the fraction defective is 0.006 and the standard deviation is 0.001. If the desired confidence level is 99.7 percent, which of the following is the resulting LCL value for the line?

Quality control charts usually have a central line and upper and lower control limit lines. Which of the following is a reason that the process being monitored with the chart should be investigated?

Consider a sampling plan with n = 40 and c = 1 and given Acceptable quality level (AQL), Lot tolerance percent defective (LTPD), producer's risk (α) and consumer's risk (β). Suppose that c is increased to 2, keeping AQL and LTPD unchanged, producer's risk (α) will

Other things remaining the same, and assuming thatis smaller than USL and larger than LSL, if the standard deviation (σ) of the process decreases, process capability index (Cpk) of the process will I. Stay the same II. Will always increase III. Will always decrease IV. Will sometimes increase

You want to determine the control lines for a p-chart for quality control purposes. If the total number of defects from all samples is 560, the number of samples is 70, and the sample size is 80, which of the following would be the standard deviation used in developing the control lines?

Sampling plans are generally displayed graphically through the use of operating characteristic (OC) curves.

Consider a sampling plan with n = 40 and c = 1 and given Acceptable quality level (AQL), Lot tolerance percent defective (LTPD), producer's risk (α) and consumer's risk (β). Suppose that c is increased to 2, keeping AQL and LTPD unchanged, consumer's risk (β) will

For which of the following should we use a p-chart to monitor process quality?

A p-chart has upper and lower control limits expressed as lines on the chart. As long as the sample values fall between these two lines, there is no need to investigate process behavior.