Exam 19: Statistical Applications in Quality Management

SCENARIO 19-8 Recently,a university switched to a new type of computer-based registration.The registrar is concerned with the amount of time students are spending on the computer registering under the new system.She decides to randomly select 8 students on each of the 12 days of the registration and determine the time each spends on the computer registering.The range,mean,and standard deviation of the times required to register are in the table that follows. -Referring to Scenario 19-8,based on the R chart,it appears that the process is out of control.

Variation signaled by individual fluctuations or patterns in the data is called

SCENARIO 19-4 A factory supervisor is concerned that the time it takes workers to complete an important production task (measured in seconds)is too erratic and adversely affects expected profits.The supervisor proceeds by randomly sampling 5 individuals per hour for a period of 10 hours.The sample mean and range for each hour are listed below. She also decides that lower and upper specification limit for the critical-to-quality variable should be 10 and 30 seconds,respectively. -Referring to Scenario 19-4,suppose the supervisor constructs an R chart to see if the variability in collection times is in-control.This R chart is characterized by which of the following?

It is not possible for the x̄ chart to be out-of-control when the R chart is in control.

SCENARIO 19-5 A manufacturer of computer disks took samples of 240 disks on 15 consecutive days.The number of disks with bad sectors was determined for each of these samples.The results are in the table that follows. -Referring to Scenario 19-5,the best estimate of the mean proportion of disks with bad sectors is .

Once the control limits are set for a control chart,one attempts to

SCENARIO 19-4 A factory supervisor is concerned that the time it takes workers to complete an important production task (measured in seconds)is too erratic and adversely affects expected profits.The supervisor proceeds by randomly sampling 5 individuals per hour for a period of 10 hours.The sample mean and range for each hour are listed below. She also decides that lower and upper specification limit for the critical-to-quality variable should be 10 and 30 seconds,respectively. -Referring to Scenario 19-4,what is the value of the CPL index?

SCENARIO 19-5 A manufacturer of computer disks took samples of 240 disks on 15 consecutive days.The number of disks with bad sectors was determined for each of these samples.The results are in the table that follows. -Referring to Scenario 19-5,a p control chart is to be made for these data.The center line of the control chart is .

Total Production Maintenance is among the tools of Lean Six Sigma.

SCENARIO 19-7 A supplier of silicone sheets for producers of computer chips wants to evaluate her manufacturing process.She takes samples of size 5 from each day's output and counts the number of blemishes on each silicone sheet.The results from 20 days of such evaluations are presented below. She also decides that the upper specification limit is 10 blemishes. -Referring to Scenario 19-7,an x̄ chart is to be used for the number of blemishes.One way to obtain the control limits is to take the grand mean and add and subtract the product of A₂ times the mean of the sample ranges.For this data set,the value of A₂ is .

The C_p index measures the potential of a process,not its actual performance.

Poke-Yoke devices is among the tools of Lean Six Sigma.

Common causes of variation are correctable without modifying the system.

Which of the following is one of Deming's 14 points?

The R chart is a control chart used to monitor a process mean.

SMED establishes ways to clean and maintain the necessary housekeeping aspects of a work environment.

C_pk > 1 indicates that the process average is exactly 3 standard deviations away from the closest specification limit.

SCENARIO 19-9 The manufacturer of canned food constructed control charts and analyzed several quality characteristics.One characteristic of interest is the weight of the filled cans.The lower specification limit for weight is 2.95 pounds.The table below provides the range and mean of the weights of five cans tested every fifteen minutes during a day's production. -Referring to Scenario 19-9,based on the x̄ chart,it appears that the process is in control.

SCENARIO 19-10 Below is the number of defective items from a production line over twenty consecutive morning shifts. -Referring to Scenario 19-10,based on the c chart,there appears to be a special cause of variation in the process.

SCENARIO 19-3 A quality control analyst for a light bulb manufacturer is concerned that the time it takes to produce a batch of light bulbs is too erratic.Accordingly,the analyst randomly surveys 10 production periods each day for 14 days and records the sample mean and range for each day. -Referring to Scenario 19-3,suppose the analyst constructs an R chart to see if the variability in production times is in-control.The R chart is characterized by which of the following?