Exam 24: Quality Control

An importer of decorative ceramic tile samples 50 tiles each day from incoming shipments. Some tiles are cracked or broken before or during transit, rendering them useless scrap. Sampling from incoming shipments for 30 days reveals that a total of 250 tiles are cracked or broken. The lower and upper control limits on the p chart for these data are

A producer of specialty products uses a variety of natural and man-made materials to make unique countertops for kitchens and baths. One product line mixes concrete and natural river stone to make countertops that are polished to a high shine revealing unique patterns. Occasionally coarse sand will result in undesirable pitting and rough spots on surfaces. Consequently, as part of its quality control efforts, 8 by 4 foot polished slabs are checked periodically for imperfections. For each slab inspected the number of imperfections (pits, rough spots, etc.) is recorded. a. What type of control chart should be used for these data? b. If the average number of imperfections per 8 by 4 foot polished slab is 2.6, calculate the centreline and control limits for the appropriate control chart.

Consider the following to answer the question(s) below: A company that fills 12 ounce soft drink bottles wishes to monitor the quality of their process. To do this, the company has taken a series of samples of 4 bottles. The overall average fill is 12.03 ounces. The average range for the samples has been 0.06 ounces. -Based on this information, what is the value of the upper control limit for the R chart?

By design, a required dimension of a part is 0.575 cm plus or minus 0.008 cm. Assume that the process producing this part is stable with a mean of 0.579 cm and standard deviation of 0.002 cm. The specification limits for this part are

Consider the following to answer the question(s) below: A company that fills 12 ounce soft drink bottles wishes to monitor the quality of their process. To do this, the company has taken a series of samples of 4 bottles. The overall average fill is 12.03 ounces. The average range for the samples has been 0.06 ounces. -Based on this information, what is the value of the upper control limit for the x-bar chart?

A paper products manufacturer coats paper with a thin film of wax. To initiate control charting, data are collected on the thickness of the coating (measured in mm) by taking twenty-five samples each of size five. The appropriate control chart for these data is the

In order to achieve higher levels of customer satisfaction, a company initiates monitoring the complaint resolution process of its customer service representatives. As a first step, the company decides to collect data on the number of unanswered calls out of the first 250 incoming to its call centre made each day. At the end of monitoring 25 days, it was found that a total of 500 incoming calls went unanswered. a. What type of control chart should be used by the company in monitoring customer satisfaction at the call centre? b. Calculate the centreline for this control chart. c. Calculate the control limits for this control chart.

A manufacturer of a particular grade of copper tubing collects data on the number of flaws occurring in 500 foot coils. Suppose they sample a total of 40 coils to initiate control charting. The average number of defects per coil is 2.5. The lower and upper control limits for the appropriate control chart for these data are

A manufacturer of a particular grade of copper tubing collects data on the number of flaws occurring in 500 metre coils. Suppose they sample a total of 40 coils to initiate control charting. The average number of defects per coil is 2.5. The appropriate control chart for these data is the

A company that manufactures health food snacks produces low sodium rice chips. To monitor the process for sodium levels, chips are selected periodically and the amount of sodium (mg) measured. For each of thirty samples consisting of 8 chips, the mean and range in sodium content is determined. The average of the means across all samples is 55 mg and the average range is 2.2 mg. a. Estimate the process standard deviation. b. Calculate the centreline and control limits for the R chart. c. Calculate the centreline and control limits for the x-bar chart.

The main cross-town transit route in a large Ontario town makes 120 trips per day. The transit authority will tolerate an average of no more than 5 late running trips per day. They wish to use a control chart to monitor the timeliness of the route. The following data were collected for 8 days. Based on this information, the values of the appropriate lower and upper control limits are

An automatic filling process is used to dispense hand sanitizer into small purse size bottles. The target weight is 75 ml. The company has initiated control charting to stabilize and improve the automatic filling process. For each of twenty-five samples consisting of four bottles, the contents were measured and the mean weight and range were determined. The average of the means across all samples was found to be 72.5 ml. and the average range was 2.75 ml. a. Estimate the process standard deviation. b. Calculate the centreline and control limits for the R chart. c. Calculate the centreline and control limits for the x-bar chart.

By design, a required dimension on a part is 0.575 cm plus or minus 0.008 cm. Assume that the process producing this part is stable with a mean of 0.579 cm and standard deviation of 0.002 cm. a. What are the specification limits on this part? b. Compute the Cp index. c. Compute the Cpk index. d. Which index is a better measure of the process capability in this instance? Explain.

A company that manufactures health food snacks produces low sodium rice chips. To monitor the process for sodium levels, chips are selected periodically and the amount of sodium (mg) measured. For each of thirty samples consisting of 8 chips, the mean and range in sodium content is determined. The average of the means across all samples is 55 mg and the average range is 2.2 mg. The lower and upper control limits for the R chart are

An importer of decorative ceramic tile samples 50 tiles each day from incoming shipments. Some tiles are cracked or broken before or during transit, rendering them useless scrap. Sampling from incoming shipments for 30 days reveals that a total of 250 tiles are cracked or broken. The centreline on the p chart for these data is

Which of the following statements is false regarding control charts?

A major airline is interested in monitoring customer satisfaction with its baggage handling process. To do so, each day the airline randomly selects 100 customers and surveys them to determine if they are satisfied or not with the service provided. After 20 samples, a total of 260 unsatisfied customers were counted. The lower and upper control limits for the appropriate control chart for these data are

An importer of decorative ceramic tile samples 50 tiles each day from incoming shipments. Some tiles are cracked or broken before or during transit, rendering them useless scrap. Sampling from incoming shipments for 30 days reveals that a total of 250 tiles are cracked or broken. a. What type of control chart should be used by the importer in monitoring the proportion of scrap tiles? b. Calculate the centreline for this control chart. c. Calculate the control limits for this control chart.

Consider the following to answer the question(s) below: A company that fills 12 ounce soft drink bottles wishes to monitor the quality of their process. To do this, the company has taken a series of samples of 4 bottles. The overall average fill is 12.03 ounces. The average range for the samples has been 0.06 ounces. -What is the correct estimate of σ?

A manufacturer of a particular grade of copper tubing collects data on the number of flaws occurring in 500 metre coils. Suppose they sample a total of 40 coils to initiate control charting. The average number of defects per coil is 2.5. a. What type of control chart should be used for these data? b. If the average number of defects per coil is 2.5, calculate the centreline and control limits for the appropriate control chart.