Exam 13: Statistical Quality Control

Standard practice in statistical process control for variables is to set control limits so that 95 percent of the sample means will fall within the UCL and the LCL.

Acceptance sampling is performed on goods that already exist to determine what percentage of items conforms to specifications.

To obtain a 99.7 percent confidence level in a p-chart, we would use a value of 3 for "z."

For R-charts, the typical sample size is 10-15.

For which of the following should we use an R-chart to monitor process quality?

AQL stands for accepting questionable lots in production quality management.

The capability index is used to gauge economic changes in service systems.

In acceptance sampling, the number of units in the sample (n) 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).

An example of assignable variation in a production system may be that a machine is not adjusted properly.

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

You are going to develop an X-bar chart based on range statistics, and you are using a sample size of 12 for your charting purposes. Which of the following is the A₂ factor for the X-bar chart?

For which of the following should we use an X-bar chart based on sample means to monitor process quality?

If the fraction defective is 0.12 based on a sample size of 16, the standard deviation used in the p-chart is about 0.08.

LTPD in acceptance sampling stands for lot tolerance for parts defective.

Measurement by attributes means taking a sample, measuring the attribute in question, and determining the level of quality in the population from which the sample was drawn.

You want to develop a three-sigma R-chart. You know the average range is 5 based on several samples of size 10. Which of the following is the resulting UCL?

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

A rule of thumb for p-charts is to use a sample size of at least 250.

You are developing an X-bar chart based on sample means. You know the standard deviation of the sample means is 4, the desired confidence level is 99.7 percent, and the average of the sample means is 24. Which of the following is your UCL?

Genichi Taguchi's view of the cost of quality is that variance is a discontinuous function.