Exam 15: Statistical Quality Control

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?

It is impossible to develop a process that has zero variability.

Assignable variations in a process are also called natural variations.

Control charts that are used to monitor processes that are measured in continuous units are classified as which of the following?

A computer diskette manufacturer is concerned that some diskettes have bad sectors that would cause a diskette to hold less information than it was intended to hold.In the past,only 5% of these diskettes have had bad sectors.If the company wishes to set 95.5% control limits based on samples of size 500,what would these limits be?

A p-chart has been developed for a particular item.In the past,4% of such items have been found to be defective.If a sample of 100 is taken,and 9 of these are found to be defective,should the process be considered out of control based on 95.5% control limits? Explain.

The inspection of cans of juice involves sampling some cans and weighing them.The overall average for the samples is 39 ounces.Each sample contains 36 cans.The standard deviation is estimated to be 2 ounces.The 99.7% lower control chart limit for the average would be

Table 15-1 -Refer to Table 15-1.Bags of chocolate candy are sampled to ensure proper weight.The overall average for the samples is 36 ounces.Each sample contains twelve bags.The average range is 1.3 ounces.The upper control chart limit for the sample averages would be

Table 15-1 -Refer to Table 15-1.The average range of a process for packaging cereal is 1.1 ounces.If the sample size is 10,find the upper control chart limit for the range chart.

Match the following. -Column 1: D₄ Column 2: Upper control limit for a range chart

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?

Variations that need not occur in production processes are referred to as

Leo Phan is the new business manager at PC Priced Right.He is concerned that his register is incorrectly ringing items.For those items sold during the last seven days,he has counted 10 that were incorrectly charged.What would be the 99.7% control limits for the number of incorrect rings per week on this process?

A coffee company is attempting to make certain that all its packaged coffee beans contain the same amount of coffee bean by weight.Over the last few days,it has taken several samples.The overall average weight of the sampled packages is 16 ounces,with an average range of 4 ounces.Each sample was of five packages.What would be the 99.7 upper and lower control limits for an -chart?

The p-chart would be useful when we

Who introduced control charts in 1924?

If we are attempting to control the diameter of bowling bowls,we will find a p-chart to be quite helpful.

The R-chart would be useful when we