Exam 15: Statistical Quality Control

Defects in computer hard-drives will usually render the entire computer worthless.For a particular model, the percent defective in the past has been 1%.If a sample size of 400 is taken, what would the 95.5% lower control chart limit be?

A company has been receiving complaints about the attitude of some sales clerks.Over a 10-day period, the total number of complaints was 360.The company wishes to develop a control chart for the number of complaints.What would the upper control limit on the number of complaints per day be for a 2 sigma (95.5%)control chart?

An x-bar chart would be appropriate to monitor the number of defects in a production lot.

P-charts and c-charts are examples of control charts for variables.

The central limit theorem provides the statistical foundation for control charts.

Which of these patterns on a control chart would require a worker to stop the process and investigate for an assignable cause?

The mean of a process can be described as

Table 15-1 -Use the data shown below and the information in Table 15-1 to develop a control chart that monitors central tendency.Use your chart to make an assessment - is the process in control?

A company is producing cylindrical blocks for a children's toy.The average diameter of a block is 3.5 inches.Sixteen blocks are inspected and the diameters are measured.The standard deviation is estimated to be 0.02 inches.What are the 99.7% upper and lower control limits for the x-bar chart?

Technically, to achieve Six Sigma quality, there would have to be fewer than ________ defects per million opportunities.

A coffee dispenser is supposed to dispense coffee into an 8 o.z.cup.The average amount of coffee filled into the cup must be below 7.9.This is best monitored by which of the following control charts?

If we are tracking quality of performance for a class of students, we should plot the individual grades on an x-bar chart, and the pass/fail result on a p-chart.

A computer software manufacturer has a toll-free telephone number that customers may use if they have problems or questions about the software.In the past, the company has averaged four calls per hour on a particular product.If a 95.5% c-chart is developed for this, what would the limits be?

Which of the following control charts is/are for attributes?

Samaje studied his control chart and noticed it had been built with repeated samples of five units and three sigma limits that were UCL = 51.71 and LCL = 38.29.What is the process standard deviation?

Which of these patterns on a control chart would require a worker to stop the process and investigate for an assignable cause?

Defects in the finish of new, custom automobiles usually require the whole body to be repainted.In one "custom" shop, the percentage of defective finishes has been 2 percent.If a sample size of 10 is taken, what should the 99.7 percent upper control limit be?

Variations that usually occur in a process are called

Statistical process control uses regression and other forecasting tools to help control processes.

Table 15-1 -Use the data shown below and the information in Table 15-1 to develop a control chart that monitors consistency.Use your chart to make an assessment - is the process in control?