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Exam 17: Process Improvement Using Control Charts

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Question 31

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A systematic method for analyzing process data in which we monitor process variation is called ______________.

A) control charting
B) sigma level capability
C) statistical process control
D) rational subgrouping

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Question 32

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The quality of an electronic component used in manufacturing cell phones is monitored with a p chart.In the last 20 days,daily samples of 75 units resulted in the following number of defective units per sample: 8,4,3,7,3,1,0,7,4,2,0,1,6,2,4,3,1,2,8,and 5.Find the LCL and UCL for the p chart.

A) [0,.1208]
B) [.0228,.0718]
C) [0,.1897]
D) [.0445,.0501]

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Question 33

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A sequence of steadily decreasing points on a control chart is called run down.

A motorcycle manufacturer produces the parts for its vehicles in different locations and transports them to its plant for assembly.In order to keep the assembly operations running efficiently,it is vital that all parts be within specification limits.One important part used in the assembly is the engine camshaft,and one important quality characteristic is the case hardness depth.Specifications state that the hardness depth must be between 3.0 mm and 6.0 mm.To investigate the process,the quality control engineer selected 25 daily subgroups of n = 5 and measured the hardness depth.The process yielded a mean of the means $\overline { \overline{ x } }$ = 4) 50 and an average range = 1.01.Assuming that the process is in statistical control,calculate the natural tolerance limits for the process.

A foreman wants to use an $\overline { \mathrm { X } }$ Chart to control the average length of the bolts manufactured.He has recently collected the six samples given below. $\begin{array} { c c c c c } \text { Sample } & & & & \\1 & 1.99 & 2.01 & 2.02 & 2.02 \\2 & 2.00 & 2.00 & 2.01 & 2.01 \\3 & 1.98 & 1.99 & 2.01 & 1.98 \\4 & 2.01 & 2.02 & 2.02 & 1.99 \\5 & 1.99 & 1.99 & 2.01 & 1.99 \\6 & 2.03 & 1.98 & 2.03 & 2.04\end{array}$ Determine the LCL and the UCL for the $\bar { X }$ Chart.

A unit that fails to meet specifications is called a _____________ unit.

A bank officer wishes to study how many customers write bad checks.To accomplish this,the officer randomly selects a weekly sample of 100 checking accounts and records the number that wrote bad checks.The numbers of customers who wrote bad checks in 20 consecutive weekly samples of 100 cardholders are,respectively,1,4,9,0,4,6,0,3,8,5,3,5,2,9,4,4,3,6,4,and 0.Find the LCL and UCL for the p chart.

How well the design of the product meets and exceeds the needs and expectations of the customers is called the quality of performance.

Use this information about 10 shipments of light bulbs: $\begin{array}{lcccccccccc}\text { Shipment } & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 \\\text { \# of defective units } & 0 & 1 & 2 & 0 & 4 & 3 & 2 & 1 & 3 & 4\end{array}$ If 200 light bulbs are selected at random from each of 10 shipments and the number of defectives in each shipment is given above,find the LCL and the UCL for the p chart.

A(n) _______ chart monitors the number of nonconformities units in a subgroup.

Suppose that $\overline { \mathrm { X } }$ And R charts based on subgroups of size 4 are being used to monitor the tire diameter.The $\overline { \mathrm { X } }$ And R charts are found to be in statistical control,with $\overline { \overline { X } } = 50.25 , \bar { R } = .8$ Inches.A histogram of the tire diameter measurements indicates that these measurements are approximately normally distributed.Find the sigma level capability of the process.

A foreman wants to use an $\overline { \mathrm { X } }$ Chart to control the average length of the bolts manufactured.He has recently collected the six samples given below. $\begin{array} { c c c c c } \text { Sample } & & & & \\1 & 1.99 & 2.01 & 2.02 & 2.02 \\2 & 2.00 & 2.00 & 2.01 & 2.01 \\3 & 1.98 & 1.99 & 2.01 & 1.98 \\4 & 2.01 & 2.02 & 2.02 & 1.99 \\5 & 1.99 & 1.99 & 2.01 & 1.99 \\6 & 2.03 & 1.98 & 2.03 & 2.04\end{array}$ Calculate the mean of the means $\overline { \overline X }$ )

Assume that 25 samples of 50 each are taken and the total number of defectives is 34.Find the LCL and UCL for the p chart.

Suppose that $\overline { \mathrm { X } }$ And R charts based on subgroups of size 4 are being used to monitor the tire diameter size of a new radial tire.The $\overline { \mathrm { X } }$ And R charts are found to be in statistical control with $\overline { \overline { X } } = 50.25 , \bar { R } = .8$ Inches.A histogram of the tire diameter measurements indicates that these measurements are approximately normally distributed.Calculate the estimate of the percentage of tires that are out of specification.

A fastener company produces bolts with a nominal (target) length of 2.00 inches.The specifications are 2.00 ± .006 inches.Determine the upper specification limit and the lower specification limit for this process.

A manufacturer of windows produces one type that has a plastic coating.The specification limits for the plastic coating are 30 and 70.From time to time the plastic coating can become uneven.Therefore,in order to keep the coating as even as possible,thickness measurements are periodically taken at four different locations on the window.15 subgroups were observed,each consisting of four thickness measurements,with the following results: mean of the means = $\overline { \overline { x } }$ = 50.05,and average range = 8.85.Calculate the center line for the R chart.

Unusual sources of process variation that can be attributed to specific reasons are called ____________ causes of variation.

Use this information about 10 shipments of light bulbs: $\begin{array}{lcccccccccc}\text { Shipment } & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 \\\text { \# of defective units } & 0 & 1 & 2 & 0 & 4 & 3 & 2 & 1 & 3 & 4\end{array}$ If 400 bulbs are selected at random from each of 10 shipments and the number of defectives in each shipment is given above,find the appropriate center line.

A manufacturer of windows produces one type that has a plastic coating.The specification limits for the plastic coating are 30 and 70.From time to time the plastic coating can become uneven.Therefore,in order to keep the coating as even as possible,thickness measurements are periodically taken at four different locations on the window.15 subgroups were observed,each consisting of four thickness measurements,with the following results: mean of the means = $\overline { \overline{ x } }$ = 50.05,and average range = 8.85.Calculate the center line for the X-bar chart.

If a company is using an $\overline { \mathcal { X } }$ chart for a given process with measurement data,it is generally not important or necessary to use an R chart or s chart.