Operations Managment
Cartons of Plaster of Paris are supposed to weigh exactly 32 oz. Inspectors want to develop process control charts. They take ten samples of six boxes each and weigh them. Based on the following data, compute the lower and upper control limits of 𝑥𝑥̅ and 𝑅𝑅 charts
UCL𝑥̅ = 32 + 0.483 × 0.52 = 32.25 LCL𝑥̅ = 32 − 0.483 × 0.52 = 31.75 UCLR = 2.004 × 0.52 = 1.04 LCLR = 0×0.52 = 0
Different Views of Quality
User-based Manufacturing-based Product-based
Assignable variations
Variation in a production process that can be traced to specific reason, special causes of variation.
The PDCA cycle stands for which of the following? A) Plan-Do-Check-Act B) Plan-Develop-Check-Accept C) Problem-Develop Solution-Check-Act D) Problem-Do-Continue-Act E) Prepare-Develop-Create-Assess
A) Plan-Do-Check-Act
A production manager at a pottery factory has noticed that about 70 percent of defects result from impurities in raw materials, 15 percent result from human error, 10 percent from machine malfunctions, and 5 percent from a variety of other causes. This manager is most likely using: A) a Pareto chart. B) a scatter diagram. C) a quality loss function. D) a cause-and-effect diagram. E) a flowchart.
A) a Pareto chart.
The goal of inspection is to: A) detect a bad process immediately. B) add value to a product or service. C) correct deficiencies in products. D) correct system deficiencies. E) all of the above
A) detect a bad process immediately.
A manager tells her production employees, "It's no longer good enough that your work falls anywhere within the specification limits. I need your work to be as close to the target value as possible." Her thinking is reflective of: A) internal benchmarking. B) Six Sigma. C) ISO 9000. D) Taguchi concepts. E) process control charts.
D) Taguchi concepts.
The number of defects after a hotel room cleaning (sheets not straight, smears on mirror, missed debris on carpet, etc.) should be measured using what type of control chart? A) x-bar chart B) R-chart C) p-chart D) c-chart E) either x-bar chart or R chart
D) c-chart
When sample measurements falls inside the control limits, it means that: A) each unit manufactured is good enough to sell. B) the process limits cannot be determined statistically. C) the process output exceeds the requirements. D) if there is no other pattern in the samples, the process is in control. E) the process output does not fulfill the requirements.
D) if there is no other pattern in the samples, the process is in control.
Techniques for building employee empowerment include: A) building communication networks that include employees. B) developing open, supportive supervisors. C) moving responsibility from both managers and staff to production employees. D) building high-morale organizations. E) All of the above are techniques for employee empowerment.
E) All of the above are techniques for employee empowerment.
Which of the following is not a typical inspection point? A) upon receipt of goods from your supplier B) when production or service is complete C) before the product is shipped to the customer D) at the supplier's plant while the supplier is producing E) after a costly process
E) after a costly process
What refers to training and empowering frontline workers to solve a problem immediately? A) just-in-time B) poka-yoke C) benchmarking D) kaizen E) service recovery
E) service recovery
An x-bar control chart was examined and no data points fell outside of the limits. Can this process be considered in control? A) Not yet, there could be a pattern to the points. B) Not yet, the R-chart must be checked. C) Not yet, the number of samples must be known. D) Yes. E)BothAandB
E)BothAandB
Seven Concepts of TQM: Taguchi Concepts
Engineering and experimental design methods to improve product and process design -Quality robustness -Target-oriented quality -Quality loss function (Even though the item is produced within specification limits, the variation in quality can be expected to increase costs as the item output moves away from its target value)
True or False? A p-chart is appropriate to plot the number of typographic errors per page of text.
False
True or False? If the process average is in control, then the process range must also be in control.
False
True or False? The purpose of process control is to detect when natural causes of variation are present.
False
Seven Concepts of TQM: Employee Empowerment
Getting employees involved in product and process improvements -Quality Circles
Seven Tools of TQM: Statistical Process Control Chart
Graphic presentation of data over time that show upper and lower limits for the process we want to control When the samples fall within the upper and lower control limits and no discernible pattern is present, the process is said to be in control with only natural variation present
Inspection
Involves examining items to see if an item is good or defective Inspection only finds deficiencies and defects - Does not correct deficiencies in process or product , nor does it change a product or increase its value - It is expensive and do not add value to the product
Seven Concepts of TQM: Just-in-Time
JIT systems are designed to produce or deliver goods just as they are needed and is related to quality in three ways: -JIT cuts the cost of quality -JIt improves quality -Better quality means less inventory and better, easier-to-employ JIT system
Statistical Process Control: All processes are subject to a certain degree of variability and control chart is to separate the two cause of variation...
Natural (common) causes of variation Special (assignable) causes of variation
C-Charts
Number of defective items vs. Number of Defects Used to control the number of defects per unit of output
Control charts
Purpose is to help distinguish between natural variations and variations due to assignable causes.
Seven Concepts of TQM: Benchmarking
Selecting best practices to use as a standard for performance
A supply chain includes
Suppliers -> manufacturers and/or service providers -> distributors, wholesalers, and/or retailers who deliver the product and/or service to -> the final customer
Quality
The ability of a product or service to meet customer needs
Samples
To measure the process, samples are taken to analyze the sample statistics.
Objective of supply chain management
To structure the supply chain to maximize its competitive advantage and benefits to the ultimate consumer
True or False? Averages of small samples, not individual measurements, are generally used in statistical process control.
True
True or False? Continuous improvement is based on the philosophy that any aspect of an operation can be improved.
True
True or False? Internal failure costs are associated with scrap, rework, and downtime.
True
True or False? Kaizen is similar to TQM in that both are focused on continuous improvement.
True
True or False? Mean charts and range charts complement one another, one detecting shifts in process average, the other detecting shifts in process dispersion.
True
True or False? Mistakes stemming from workers' inadequate training represent an assignable cause of variation.
True
True or False? Some degree of variability is present in almost all processes.
True
True/False. A process is said to be operating in statistical control when the only source of variation is common (natural) cause.
True
True/False. The idea is that each supplier, process, and employee treats the next step in the process as the customer
True
A Six Sigma program has how many defects per million? A) 3.4 B)34 C) 1000 D) 6 times the standard deviation E) 2700
A) 3.4
Which of the four major categories of quality costs is particularly hard to quantify?
external failure costs
Natural Variations
- Affects every production process -Can be described as distribution -For any distribution there is a central tendency (mean) and dispersion (standard deviation) -As long as the distribution remains within specified limits, it is in control.
Inspection of Attributes
- Classifies Items as being either good or defective, acceptable or unacceptable - Does not address degree of failure
Capable process must have...
- Cp of at least 1.0 -Cpk of at least 1.0
Inspection of Variable
- Measures dimensions such as weight, speed, size, or strength - Falls within an acceptable range
Control Charts for Attributes
-Attributes are typically categorical -Percent defective (p-chart) -Number of defects (c-chart)
Six Sigma DMAIC approach
-Define -Measure -Analyze -Improve -Control
Outcomes of taking a sample
-If only natural causes of variation are present, the output of a process forms a distribution that is stable over time and is predictable -If assignable causes are present, the process output is not stable over time and is not predicable
Seven Concepts of TQM: Six Sigma
-In a statistical sense, it describes a process, product, or service with an extremely high capability (99.9997% accuracy), 3.4 defects per million opportunities (DPMO) -Strategy focused on total customer satisfaction -discipline follows DMAIC -Set of 7 tools: check sheets, scatter diagrams, cause-and-effect diagrams, Pareto charts, flowcharts, histograms, and statistical process control
Seven Concepts of TQM: Continuous improvement
-Never-ending process of continuous improvement -PDCA (plan, do, check, act) stress the continuous nature of improvement. -Kaizen> ongoing process of unending improvement. -TQM and zero defects describe continuous improvement.
The Flow of Activities Necessary to Achieve Total Quality Management
-Organizational Practices (organizational culture fosters quality -Quality Principles (understanding of the principles of quality) -Employee Fulfillment (engaging employees to implement) -Customer Satisfaction
Control Charts for Variables
-Variables have continuous dimensions -X(bar)-chart tracks changes in the central tendency (mean) -R-chart tracks range *charts are used together
Seven Concepts of TQM
1) Continuous improvement 2) SixSigma 3) Employee empowerment 4) Benchmarking 5) Just-in-time (JIT) 6) Taguchi concepts 7) Knowledge of TQM tools
When and Where to Inspect
1. At the supplier's plant while the supplier is producing 2. At your facility upon receipt of goods from your supplier 3. Before costly or irreversible processes 4. During the step-by-step production process 5. When production or service is complete 6. Before delivery to your customer 7. At the point of customer contact
Range
=Difference between smallest and largest values in sample.
Seven Tools of TQM:Cause-and-Effect Diagram
A tool that identifies process elements (causes) that may effect an outcome Four categories: material, machinery/equipment, manpower, methods, Also known as fish-bone chart
Seven Tools of TQM: Flowchart (Process Diagram)
A block diagram that describes the steps in a process
Seven Tools of TQM: Histogram
A distribution showing the frequency of occurrences of a variable
Seven Tools of TQM: Pareto Chart
A graph to identify and plot problems or defects in descending order of frequency visualization of summarizing data
Internal Benchmarking
A natural approach. When an organization is large enough to have many divisions or business units.
SERVQUAL technique
A popular measurement scale for service quality that compares service expectations with service performance
If a sample of items is taken and the mean of the sample is outside the control limits, the process is: A) likely out of control and the cause should be investigated. B) in control, but not capable of producing within the established control limits. C) within the established control limits with only natural causes of variation. D) monitored closely to see if the next sample mean will also fall outside the control limits. E) producing high quality products.
A) likely out of control and the cause should be investigated.
The "four Ms" of cause-and-effect diagrams are: A) material, machinery/equipment, manpower, and methods. B) material, methods, men, and mental attitude. C) named after four quality experts. D) material, management, manpower, and motivation. E) mentality, motivation, management, and manpower.
A) material, machinery/equipment, manpower, and methods.
Seven Tools of TQM: Check Sheet
An organized method of recording data
A manager wants to build 3-sigma x-bar control limits for a process. The target value for the mean of the process is 10 units, and the standard deviation of the process is 6. If samples of size 9 are to be taken, what will be the upper and lower control limits, respectively? A)-8and28 B) 16 and 4 C) 12 and 8 D)4and16 E) 8 and 12
B) 16 and 4
The process of identifying other organizations that are best at some facet of your operations and then modeling your organization after them is known as: A) continuous improvement. B) benchmarking. C) Taguchi concepts. D) employee empowerment. E) corporate responsibility.
B) benchmarking.
Poka-yoke is the Japanese term for: A) card. B) foolproof. C) continuous improvement. D) fishbone diagram. E) just-in-time production.
B) foolproof.
ars of pickles are sampled and weighed. Sample measures are plotted on control charts. The ideal weight should be precisely 11 oz. Which type of chart(s) would you recommend? A) p-chart B) c-chart C) both an x-bar chart and an R-chart D) an x-bar chart, but not an R-chart E) both a p-chart and a c-chart
C) both an x-bar chart and an R-chart
The number of late insurance claim payouts per 100 should be measured with what type of control chart? A) x-bar chart B) R-chart C) p-chart D) c-chart E) either p-chart or c-chart
C) p-chart
What is a popular measurement scale for service quality that compares service expectations with service performance? A) COQ B) SPC C) KAIZEN D) SERVQUAL E) TQM
D) SERVQUAL
R-Chart
a chart used to monitor process variability
TQM stresses
a commitment by management to have a continuing companywide drive toward excellence in all aspects of products and services that are important to the customer
"Making it right the first time" is:
a manufacturing-based definition of quality.
Process Capability
a measure of the relationship between the natural variation of the process and the design specifications.
xbar chart
a quality control chart for variables that indicates when changes occur in the central tendency of a production process
Total quality management (TQM)
a quality emphasis that encompasses entire organization, from supplier to customer.
Implications of Quality
company reputation product liability global implications
The process must first be brought into statistical control by...
detecting and eliminating special (assignable) causes of variation
Managing quality helps build successful strategies of
differentiation, low cost, and response
Quality helps firms
increase sales and reduce costs increase profitability
An operations manager's objective
is to build a total quality management system that identifies and satisfies customer needs
Costs of Quality (COQ)
prevention costs- reducing potential for defective parts or service. appraisal costs-evaluating products, processes, parts, and services. internal failure costs-defective parts or services before delivery external failure costs- defective parts or services discovered after delivery
Two popular measures for quantitatively determining if a process is capable
process capability ratio (Cp) and process capability index (Cpk)
Objective of a process control system
provide a statistical signal when assignable causes of variation are present
Identifying and meeting customer expectations
requires an emphasis on TQM if a firm is to compete as a leader in world markets
Seven Tools of TQM: Scatter Diagram
show the relationship between two measurements
Supply chain management
the coordination of all supply chain activities, starting with raw materials and ending with a satisfied customer.
Inspection goal
to detect a bad process immediately
The normal distribution is defined by two parameters, the mean and standard deviation. The x-chart and R-chart...
track changes in these two parameters both charts are required to track the process accurately
Source Inspection (source control) may be assisted with the use of...
• Poka-yoke is a foolproof devices or techniques designed to pass only acceptable products • Checklists are a type of poka-yoke to help ensure consistency and completeness in carrying out a task
Source Inspection (source control)
• The best inspection can be thought of as no inspection at all; this "inspection" is always done at the source - It is just doing the job properly with the operator ensuring that this is so
Service quality is judged based on whether it meets expectations
• The tangible component of services is important - How accurate, clear the checkout bill is at the hotel - How warm the food is at Taco Bell - How well the car runs after pick it up at the repair shop • The service process is important- Reliability and courtesy are part of the process • Service quality is judged based on whether it meets expectations - Don't promise more than you can deliver • Exceptions will occur
Seven Concepts of TQM: 7 TQM Tools
• Tools for Generating Ideas - Check Sheet -Scatter Diagram -Cause-and-Effect Diagram • Tools to Organize the Data -Pareto Chart -Flowchart (Process Diagram) • Tools for Identifying Problems - Histogram - Statistical Process Control Chart