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COB 300 Operations Test 2 (Pal) Questions and Answers
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COB 300 Operations Test 2 (Pal) Questions and Answers
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COB 300 Operations Test 2 (Pal)Questions and Answers
Phases of Quality Assurance - Answers -1. Acceptance sampling: inspection
before/after production (least progressive)
2. Process control: inspection and corrective action during production
3. Continuous improvement: quality built into the process (most progressive)
Inspection - Answers -An appraisal activity that compares goods or services to a
standard
Inspection Issues - Answers -1. How much to inspect and how often
2. At what points in the process to inspect
3. Whether to inspect in a centralized or on-site location
4. Whether to inspect attributes or variables
Where to inspect in the process - Answers -1. Raw materials and purchased parts
2. Finished products
3. Before a costly operation
4. Before an irreversible process
5. Before a covering process
Centralized vs On-Site Inspection - Answers -Effects on cost and level of disruption are
major considerations
Centralized - Answers --Specialized tests that may best be completed in a lab
-More specialized testing equipment
-More favorable testing environment
On-Site Inspection - Answers --Quicker decisions are rendered
-Avoided introduction of extraneous factors
-Quality at the source
two basic questions concerning variability - Answers --Issue of Process Control
-Issue of Process Capability
Issue of process control - Answers -Are the variations random? If nonrandom variation
is present, the process is said to be unstable.
Issue of Process Capability - Answers -Given a stable process, is the inherent variability
of the process within a range that conforms to performance criteria?
,Steps required for effective control - Answers --Define: What is to be controlled?
-Measure: How will measurement be accomplished?
-Compare: There must be a standard of comparison
-Evaluate: Establish a definition of out of control
-Correct: Uncover the cause of nonrandom variability and fix it
-Monitor: Verify that the problem has been eliminated
Statistics to manage quality - Answers --Requires less labor (reduces costs)
-Useful when testing destroys products
Categories of statistical tools - Answers --Statistical process control
-Acceptance sampling
Statistical process control - Answers -Assesses whether or not an ongoing process is
preforming within established limits
Acceptance Sampling - Answers -Assesses the quality of parts or products after they
have been produced
Statistical Process Control (SPC) - Answers -A quantitative method for determining
whether a particular process is in or out of control
Process Variations - Answers --Random (common cause) variations
-Assignable (special cause) variations
Random (common cause) variation - Answers -Natural variation in the output of a
process, created by countless minor factors
Assignable (special cause) variation - Answers --Variations whose source can be
identified
-Easy to control/correct
Why are samples taken? - Answers -To determine whether assignable variations are
present in the output of a process
Central Limit Theorem - Answers -Sample means will be normally distributed no matter
whatever distributions the samples follow
Types of Data - Answers --Variable: data that measures a particular product
characteristic (continuous) (length or width)
-Attribute: data that counts items (discrete) - number of defective items in a sample
Variable Charts - Answers -- R chart
- X-bar chart
, Attribute Charts - Answers --p-chart
-c-chart
Fundamental concept in Control Charts - Answers --95.44% of all sample means fall
within +- 2 standard deviations
-99.74% of all sample means fall within +- 3 standard deviations
Generic Control Charts - Answers --Have a center line that is the overall average
-Have limits above and below the center line at +- 3 standard deviations (usually)
Process centering - Answers -- X bar chart
- X bar is a sample mean
- Size of each sample is n
Process Dispersion (consistency) - Answers -- R chart
- R is sample mean
X Bar Charts - Answers --Center line is the grand mean (x double bar)
-Points are X bars
Range (R) Charts - Answers --Center line is the grand mean (R bar)
-Points are R
Run tests - Answers --Even if a process appears to be in control, the data may not
reflect a random process
-Even if points are in the control limits the process must be random
C Charts - Answers --Used to count defects in samples of constant size
-Center line is the grand mean (c bar)
-Number of samples is m
P Charts - Answers --Used to track a proportion (fraction) defective
-Center line is the grand mean (p bar)
-Number of sample is m
-Size of each sample is n
Improving Process Capability - Answers --Simplify
-Standardize
-Mistake-proof
-Upgrade equipment
-Automate
Centered Process - Answers --3 sigma: defects 2,700 parts per million
-6 sigma: defects 0.002 parts per million
Non-Centered Process - Answers --3 sigma: defects 67,000 parts per million
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