Exam 17: Statistical Applications in Quality Management

TABLE 17-8 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 Table 17-8,based on the R chart,it appears that the process is out of control.

TABLE 17-2 A political pollster randomly selects a sample of 100 voters each day for 8 successive days and asks how many will vote for the incumbent.The pollster wishes to construct a p chart to see if the percentage favoring the incumbent candidate is too erratic. -Referring to Table 17-2,what is the numerical value of the lower control limit for the p chart?

Common causes of variation are correctable without modifying the system.

TABLE 17-7 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. -Referring to Table 17-7,construct an chart for the number of blemishes.

TABLE 17-10 Below is the number of defective items from a production line over twenty consecutive morning shifts. -Referring to Table 17-10,the c chart suggests that the special cause of variation must be incorporated into the process to become part of the permanent ongoing process.

TABLE 17-4 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 Table 17-4,what percentage of the time it takes workers to complete an important production task will fall inside the specification limits?

TABLE 17-7 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. -Referring to Table 17-7,an chart is to be used for the number of blemishes.The lower control limit for this data set is ________,while the upper control limit is ________.

TABLE 17-7 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. -Referring to Table 17-7,what is the value of d₂ factor?

A process capability is estimated by the percentage of product or service that fall outside the specification limits.

TABLE 17-3 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 Table 17-3,suppose the analyst constructs an chart to see if the production process is in-control.What is the upper control limit (UCL)for this chart?

The CPL and CPU indexes are used to measure a process's actual performance rather than its potential.

TABLE 17-4 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 Table 17-4,what is the value of d₂ factor?

Common causes of variation represent variation due to the inherent variability in the system.