Part 4: Product and Process Control Flashcards
An employee works in an area of a facility where tools are painted. Which of the following would this employee find in the control plan for the process of painting stools?
A) The sample size and frequency of sampling to monitor the painting process
B) A detailed description of the painting process
C) A list of the machines used to paint the tools
D) All of the above
D - All of the above
Control plans typically include the following:
A description of the process
Any equipment used in the process
Reference drawing numbers,
The process characteristic that is being controlled
How the process characteristic should be evaluated,
The sampling plan
The method of control
Reaction plan if the process goes out of control
Which of the following would you typically find in a reaction plan for a process?
A) Sampling plan
B) Control chart
C) Detailed methods to contain questionable products
D) Gage R&R study
C - Detailed methods to contain questionable products
A reaction plan typically contains four elements: containment, diagnosis, verification, and disposition. The reaction plan should therefore include specific direction for the operators on how to contain products that are suspected of being nonconforming or out of spec.
Why are work instructions an important component of process control
A) The explain sampling procedure
B) They identify bottlenecks in a process
C) They help reduce process errors
D) They help to manage quality costs
C - They help reduce process errors
Work instructions provide details of a process for those who operate the process. Providing detailed instruction help eliminate errors by providing all required machine settings, setup instructions, and visual aids.
Why is it important to identify materials used in producing a product?
A) To help manufacturers reduce risk
B) To save money
C) To help ensure product reproducibility
D) None of the above
A - To help manufacturers reduce risk
Knowing where material come from also gives the manufacturers the ability to trace the product. This help to reduce exposure to additional risks.
Which of the following is one of the most effective methods of accounting for and tracking product materials?
A) Control charts
B) OC curves
C) Paper move tags
D) Radio frequency identification
D - Radio Frequency Identification
Radio frequency identification (RFID) is a common method used to identify and track materials using bar codes, scanners, an RFID receivers. RFID tags allow manufacturers to maintain detailed information about materials as well.
A food company is planning to release a new type of cookie. At what stage in the process should the company consider tracing the cookie’s components?
A) Before the release of the cookie to the public
B) After any inquires form customers
C) At the beginning of the cookie’s development
D) Only when there is an increase in nonconforming cookies.
C - At the beginning of the cookie’s development
Product identification and traceability should begin when the process is being designed. Including traceability from the start will ensure adequate quality of the cookie and help reduce recall risks.
Keeping nonconforming products from being mixed with good/conforming products within a manufacturing plant is known as:
A) Compliance
B) Material segregation
C) Material review
D) Defect classification
B - Material segregation
Material segregation ensure that nonconforming products are not mixed with conforming products
A recall due to a brake malfunction on an automobile was issue by a car company. How would the company classify this type of defect?
A) Minor defect
B) Major defect
C) Serious defect
D) Critical defect
D - Critical defect
A brake malfunction in a car could lead directly to a sever customer injury; therefore, this defect would be classified as critical.
Customers have complained about the battery life for a new line of computers released. How would the computer company classify this type of product defect?
A) Minor defect
B) Major defect
C) Serious defect
D) Critical defect
B - Major defect
The poor battery life of the computer reduces the usability of the product but will not likely lead to and injury or significant economic loss. Therefore, the company would classify this as a major defect.
What purpose does the material review board of a company serve?
A) Oversee the traceability of a product
B) Develop sampling plans for product materials
C) Identify the source of all product components
D) Determine corrective action for nonconforming components
D - Determine corrective action for nonconforming components
The material review board MRB determines the appropriate corrective action to take in the case that nonconforming components are discovered. it also determines any additional actions to take to prevent similar nonconformities in the future.
Acceptance sampling is most appropriate for inspecting products when:
A) the product is complex
B) the fraction of nonconforming products is unknown
C) there are high inspection costs
D) the cost of making a wrong decision is high
C - there are high inspection costs
The acceptance sampling is most appropriate when the inspection costs are high or when destructive inspection is the only method of inspection. Acceptance sampling is also appropriate when the inspection of a product is monotonous and causes inspector fatigue, which could lead to an increase in inspection errors.
A disadvantage of sampling inspection compared to 100% inspection is:
A) sampling has lower inspection costs
B) sampling is more time intensive than 100% inspection
C) sampling emphasizes that the supplier is concerned with quality
D) rejecting a lot that conforms to specification as a result of variability in sampling.
D - rejecting a lot that conforms to specification as a result of variability in sampling
Sampling inspection has several advantages as it saves time and energy compared to 100% inspection. However, there is variability inherent in sampling. Therefore, there are changes of making typing ) and type II errors: rejecting lots that conform to the quality specification or accepting lots that do not conform to quality specifications.
Which of the following tools is most appropriate when evaluating a sampling plan?
A) Scatter plot
B) Operating characteristic (OC) curve
C) Process map
D) Affinity diagram
B - Operating characteristic (OC) curve
An operating characteristic (OC) curve display the probability of accepting lot at varying levels of percentage nonconforming, It provides a simple, graphical way to evaluate a sampling plane. Scatter plots are appropriate to analyze the relationship between two variable. A process map is used to help understand the step is of a process. Affinity diagrams are useful as a planning tool to help organize ideas generated by a group.
A company requires a part on a small lot-by-lot basis. On which of the following probability distributions should the OC curve of the sampling plan be based?
A) Hypergeometric distribution
B) Binomial distribution
C) Poisson distribution
D) Normal distribution
A - Hypergeometric distribution
Because the products are received on a lot-by-lot basis and are not part of a continuous process, the OC curve should be based on the hypergeometric distribution. This OC curve is called a type A OC curve. Type B OC curves are used to evaluate a sampling plan for a continuous process or for a process that has a large lot size. Type B OC curves are developed using the binomial or Poisson distributions.
A company is deciding between two competing sampling plans for a product they receive from a manufacturer. The diagram below display the OC curves for these two sampling plans.
[Both lines look like second half of normal distribution, Solid line above dotted line, and dotted line has steeper slope and flatten sooner than the solid line]
Compared to the solid line, the dashed OC curve:
A) is better for the company
B) will accept lot with a higher probability
C) is better for the manufacturer
D) None of the above
A - is better for the company.
The dashed OC curve is better for the consumer. As the percentage nonconforming increases, the probability of accepting the lot decreases much faster compared to the other OC curve. This means that the company will accept fewer unacceptable lots from the producer.
Consider a sampling plan with n = 45 and c = 2. Given that the percentage nonconforming is 0.05 and a binomial distribution is appropriate, what is the probability of accepting the lot?
A) 0.3923
B) 0.6093
C) 0.6077
D) 0.3350
C - 0.6077
In acceptance sampling, what does the acronym “LTPD” mean?
A) The quality level
B) The poorest quality in an individual lot that should be accepted
C) The average quality of outgoing product
D) The worst tolerable process average of a continuing series of lots.
B - The poorest quality in an individual lot that should be accepted
LTPD is the lot tolerance percent defective. it is expressed in percentage defective. It is the worst quality level in an individual lot that should be accepted when submitted for acceptance sampling. Consequently, the LTPD has a low probability of acceptance.
Type I error in hypothesis testing corresponds to which of the following in acceptance sampling?
A) Consumer’s risk
B) Producer’s risk
B - Producer’s risk
A type I error in hypothesis testing is the probability of rejecting the null hypothesis when in fact the null hypothesis is true. Therefore, type I error corresponds to the producer’s risk in acceptance sampling: the probability that a lot is rejected when in fact the lot is within the acceptable quality level.
Consider a sampling plan with n = 45 and c = 2. Given that the percentage nonconforming is 0.05 and a lot size assumed to be infinite, what is the average outgoing quality?
A) 0.6077
B) 0.3923
C) 0.0304
D) 0.9696
C = 0.0304
In an acceptance sampling plan, how does the probability of acceptance change as the sample size increases, assuming the acceptance number and lot size are held constant?
A) Pa Increases
B) Pa decreases
C) Pa stays constant
D) Not enough information provided
B - Pa decreases
As the sample size increases, the probability of acceptance decreases. Consider for example, and infinite lot size, and acceptance number c=1, and fraction nonconforming p=0.05. For various sample sizes n, we have the following probability of acceptance:
Sample size (n) Pa 2 0.9975 5 0.9774 10 0.9139 20 0.7358
Holding all else equal, which factor has the least effect on the OC curve?
A) The lot size, N
B) The sample size, n
C) The acceptance number, c
D) None of the above
A - the lot size , N
The lot size, N, has the smallest effect on the OC curve compared to the acceptance number c and the sample size n
In acceptance sampling, what is the AOQL?
A) The minimum average outgoing quality limit
B) The maximum average outgoing quality limit
C) The average quality of outgoing products
D) The poorest quality in an individual lot that should be accepted
B - The maximum average outgoing quality limit
AOQL stands for the average outgoing quality limit and is the maximum average outgoing quality level for a given sampling plan. The AOQL is the highest value on an AOQ curve.
At a particular factory, testing whether a lot obtained by a supplier is acceptable requires destructive testing. What type of sampling method is most appropriate?
A) Continuous sampling
B) Single sampling
C) Double sampling
D) Sequential sampling
D - Sequential sampling
Sequential sampling is advantageous when testing samples is costly or destructive. This type of sampling plan greatly reduces the sample sizes necessary for acceptance sampling.
What is a potential disadvantage of single sampling plans?
A) They do not use tightened inspection
B) They are hard to administer in practice
C) The sample size is adjustable for changes in incoming product quality
D) All of the above
A - They do not use tightened inspection
The sample size of a single sampling plan does not change, regardless of changes in incoming product quality levels. Therefore, reduced or tightened changed in incoming product quality levels. Therefore, reduced or tightened inspection is not implemented with single sampling plans, which typically reduces sampling costs.
The attribute sampling plan for a specific product utilizes an acceptance value of 2 and rejection value of 5. The inspector discovers two defective items in the current sample. What is the next appropriate actions?
A) Accept the lot since the number of defective items does not exceed the Ac value.
B) Accept the lot since the number of defective items is less than the Re value
C) Reject the lot since the number of defective items is not less than the Ac value
D) Draw another sample.
A - Accept the lot since the number of defective items does not exceed the Ac value
When using a double sampling plan, after you take the first sample, you will either accept the lot, reject the lot, or draw another sample. If the number of defective items in the first sample, d1, is less than or equal to the acceptance number, then you accept the lot. If d1 is greater than the rejection number value, then you reject the lot. If d1 is more than the acceptance number but less than the rejection number, then you draw another sample. In this case, d1 = 2 = Ac. Therefore the lot is accepted, and another sample does not need to be drawn.
A double sampling plan is implemented with the follow parameters:
n1 = 50 n2 = 75 c1 = 1 c2 = 3 r1 = 4 r2 = 6
What is the probability that a decision is made (to accept or reject the lot) on the first sample if the percentage nonconforming, p, is equal to 0.10?
A) 0.2165
B) 0.9221
C) 0.7835
D) 0.8614
C = 0.7835
A double sampling plan is implemented with the follow parameters:
n1 = 50 n2 = 75 c1 = 1 c2 = 3 r1 = 3 r2 = 4
What is the average sample number for this sampling plan if the percentage nonconforming, p, is equal to 0.10?
A) 50
B) 125
C) 109
D) 67
D = 67
When compared with sampling plans with equal protection, the average sample number of double sampling plans generally is:
A) smaller when the quality is poor
B) larger when the quality is poor
C) larger when the quality is near the indifference level (p =.50)
D) None of the above
B = larger when the quality is poor
When the quality of the lots is very good or very poor, the average sample size will generally be smaller compared with other sampling plans with equal protection. This is because the probability of making a decision on the first sample will then to be higher, and thus fewer second samples are required. When the quality of the lots is near the indifference level (p = 0.50), the average sample number of double sampling plans is rarely larger.
Which of the following types of sampling is not allowed in ANSI/ASQ Z1.4-2003 (R2013)?
A) Single sampling
B) Sequential sampling
C) Double sampling
D) Multiple sampling
B = Sequential sampling
ANSI/ASQ Z1.4-2003 (R2013) allows for single sampling, double sampling, and multiple sampling.
A lot size of 1500 is to be inspected using ANSI/ASQ Z1.4-2003 (R2013). The AQL is 0.40%. What is the required sample size for a single sampling plan (normal, level II inspection)?
A) 50
B) 80
C) 125
D) 200
C = 125
Given that the lot size is 1500, the sample size code letter from the ANSI/ASQ Z1.4-2003 (R2013) sampling tables for normal, level II sampling is K. Regardless of the AQL level, the required sample size is n = 125.
A lot size of 500 is to be inspected using ANSI/ASQ Z1.4-2003 (R2013). The AQL is 0.65%. What are the required sample size, acceptance number, and rejection number for a single sampling plan (normal, level II inspection)?
A) n = 50, Ac = 0, Re = 1
B) n = 50, Ac = 1, Re = 2
C) n = 80, Ac = 0, Re = 1
D) n = 80, Ac = 1, Re = 2
B = n = 50, Ac = 1, Re = 2
Given that the lot size is 500, the sample size code letter from the sampling tables for normal, level II sampling is H. Using the table, the required sample size is 50. Using the AQL of 0.65%, the downward arrow point to the sampling plan for code letter J. Therefore, the acceptance number is 1 and the rejection number is 2.
A lot size of 200 is to be inspected using ANSI/ASQ Z1.4-2003 (R2013). The AQL is 0.65%. What are the required sample sizes for a double sampling plan (normal, level II inspection)?
A) 20, 40
B) 13, 13
C) 20, 20
D) 32, 32
C = 20, 20
Given that the lot size is 200, the sample size code letter from the sampling tables for normal, level II sampling is G. Using the table for double sampling plans for normal inspection , and the same size code letter G, the sample size required is 20 for both the first and second sample regardless of the AQL.
A lot size of 400 is to be inspected using ANSI/ASQ Z1.4-2003 (R2013). The AQL is 0.65%. For the first sample of a double sampling plan (normal, level II inspection), what are the acceptance and rejection numbers?
A) Ac = 1, Re = 4
B) Ac = 1, Re = 2
C) Ac = 0, Re = 3
D) None of the above
D = None of the above
Given that the lot size is 400, the sample size code letter from the sampling tables for normal, level II sampling is H. Using the table for double sampling plans for normal inspection , and the same size code letter H, and AQL = 0.65%, the downward arrow point to the sampling plan for code letter J. Therefore, the acceptance number for the first sample is 0 and the rejection number of the first sample is 2
AOQL is used to build which kind of sampling plan?
A) Single sampling plan
B) Dodge-Romig sampling tables
C) Double sampling plan
D) Sequential sampling plans
B = Dodge-Romig sampling tables
Dodge-Romig tables use the AOQL and LTPD for plan selection. The plans are designed to minimize average total inspection.
An advantage of variables sampling plans compared to attribute sampling plans is that variables sampling plans:
A) Require smaller sample sizes with equal protection compared to attribute sampling plans
B) are easier to implement
C) can monitor multiple quality characteristics at once
D) are less expensive to implement
A = require smaller sample sizes with equal protection compared to attribute sampling plans.
Variables control charts offer equal protection compared to an attribute sampling plan with a much smaller sample size. Hoever, they are generally more expensive to implement and are much harder to administer. They also can only monitor one quality characteristic at a time.
A lot of 100 items is submitted for inspection under level II, normal inspection with AQL = 0.65%. Both upper and lower specification limits are specified for this system. What sample size is required for this sampling plan?
A) 5
B) 7
C) 10
D) 20
C = 10
The sampling table gives sample size code letter F. This code letter corresponds to a sample size of 10 regardless of the AQL level.
A lot of 20 items is submitted for inspection under level II, normal inspection with AQL = 1.00%. The required sample size for this sampling plan is 4. the results of the four measurements are: 51, 47, 45, 39.
Does this lot meet the acceptance criteria? the upper and lower specification limits for this process are 52 and 37 respectively.
A) Yes, since the total percentage nonconforming is less than the maximum allowable.
B) No, since the total percentage nonconforming is less than the maximum allowable.
C) Yes, since the total percentage nonconforming is more than the maximum allowable.
D) No, since the total percentage nonconforming is more than the maximum allowable.
D = No, since the total percentage nonconforming is more than the maximum allowable.
Which of the following parameters is not required to determine a sequential sampling plan?
A) Producer’s risk
B) Consumer’s risk
C) Rejectable quality level
D) AOQL
D = AOQL
To determine a sequential sampling plan, the producer’s risk (α), the consumer’s risk (β), the acceptable quality level (AQL=p1), and the rejectable or limited quality level (RQL=p2) are required.
A sequential sampling plan has the following parameters: α = 0.01 AQL = 0.05 β = 0.15 RQL = 0.25
Which of the following statements about this sampling plan is true?
A) The plan has a 1% chance of rejecting a lot that is 25% defective
B) The plan has a 1% chance of rejecting a lot that is 5% defective
C) The plan has a 15% chance of rejecting a lot that is 25% defective
D) The plan has a 15% chance of rejecting a lot that is 25% defective
C = The plan has a 15% chance of rejecting a lot that is 25% defective
β = 15% is the consumer’s risk and is the probability of accepting a lot that does not meet the quality levels.
RQL = 25% is the rejectable (or unacceptable) quality level.
Therefore, the plan has a 15% chance of accepting a lot that is 25% nonconforming.
A sequential sampling plan has the following parameters: α = 0.01 AQL = 0.05 β = 0.15 RQL = 0.25
What is the equation for the reject line for this sampling plan?
A) 0.1281n - 1.0224
B) 0.1281n - 2.4069
C) 0.1281n + 2.4069
D) None of the above
C = 0.1281n + 2.4069
A sequential sampling plan has an accept line defined as:
Accept line = 0.1043n - 1.2486
For a sample size n=10, what is the acceptance number?
A) 0
B) 1
C) 2
D) None of the above
D = None of the above
Plugging n=10 into the equation 0.1043n - 1.2486 equals -0.2056
Since the acceptance number is negative, acceptance is not possible for this sample size additional samples must be taken
A sequential sampling plan has a reject line defined as:
Reject line = 0.1576n + 1.9397
By what sample unit would you be able to reject a lot given this reject line?
A) 2
B) 3
C) 13
D) None of the above
B = 3
Given the reject line, Rejection of a lot is not possible when the rejection number is greater than the sample number. Therefore, rejection of the lot will be possible when the rejection number is less than the sample number.
We can find this sample number since we require:
0.1576n + 1.9397 > n
n > 2.303
Why is sampling integrity important?
A) To be able to accurately read an OC curve
B) To ensure that a product has not been contaminated during inspection
C) to have the most efficient process
D) To reduce the amount of sampling required
B = To ensure that a product has not been contaminated during inspection
Sample integrity is necessary to ensure that a product has not been misused or contaminated and to ensure that sampling is accurate to the entire lot of products.
Which of the following is not a method used to maintain sample integrity?
A) Uniquely identifying a batch of products
B) Tracking changes made to a product
C) Implementing 100% inspection
D) Maintaining descriptive directions used to create a product
C = Implementation of 100% inspection
To maintain sample integrity, you can use batch control (which includes documenting the steps used to create the product, giving unique identification number to each batch produced, and maintaining a log listed the among of each material inserted into the batch), change control ( which involves classifying and tracking changes made to a product), and configuration control ( an extension of change control)
Which of the following is a result of dimensional inspection of a product?
A) Improved quality of the product
B) Conformity to customer aesthetic requirements
C) Determination of a conforming or nonconforming product
D) None of the above
C = Determination of a conforming or nonconforming product
Dimensional inspection involves measurement of a product to determine whether the product meets required specifications. Inspecting a product to determine if it meets the specifications, however, does not determine its quality. The quality of the product will depend on the engineering design and how it was manufactured.
Which of the following provides the most precise angular measurement?
A) Protractor
B) Bevel protractor
C) Square
D) Sine bar
D = Sine bar
A sine bar is more precise for measuring angles as compared to protractors, bevel protractors, or squares.
The outside dimensions of a part are inspected for conformance to product specifications. Which of the following measuring tools is most appropriate for this measurement?
A) Steel ruler
B) Plug gage
C) Snap gage
D) Sine bar
C = snap gage
Gages are used to determine conformance (or nonconformance) of a part’s dimensions to specifications. Specifically, snap or ring gages are used to check outside dimensions; plug gages are used to check inside dimensions.
A part was inspected using a go/no-go gage. The part did not mate with either end of the gage. Did the part pass the inspection?
A) No, the part should be rejected.
B) Yes, the part should be accepted.
C) Not enough information provided
A = No, the part should be rejected
A part passes inspection with a go/no-go gage if the part mates with the go end and does not mate with the no-go end. Since this part did not mate with either end, it did not pass the “go” inspection. Therefore, the part should be rejected.
Which of the following methods is the most common for surface measurements?
A) Reflectance meters
B) Optical interference
C) Pneumatics
D) Stylus averaging
D = Stylus averaging
Using a stylus to measure an average electrical signal is the most common method of surface measurement because it is fast, repeatable, interpretable, and relatively inexpensive.
A key component of a part is round in shape. Which of the following measurement tools is most appropriate to measure this component?
A) Ring gage
B) Vernier calipers
C) Precision spindle
D) Dial indicator
C = Precision spindle
Precision spindle instruments are used for roundness measurements. Calipers are used for linear measurements, ring gages are used to assess specification conformance of outside dimensions, and dial comparators are used to check operations (for example, verify alignments).
The maximum tensile strength a particular part can withstand is an important quality characteristic of this part. Which of the following is most appropriate to test this quality characteristic?
A) 100% inspection
B) Screening inspection
C) Coordinate measuring machine
D) Nondestructive testing
D = Nondestructive testing
Measuring the maximum tensile strength of a part would be destructive to the part. Therefore, screening inspection or 100% inspection is not appropriate; nondestructive testing is required.
Which of the following nondestructive tests can only be used on parts made of iron and steel?
A) Liquid penetration testing
B) Magnetic particle testing
C) Eddy current testing
D) Ultrasonic testing
B = Magnetic particle testing
Magnetic particle testing is used on parts that can be magnetized; therefore, magnetic particle testing can be done only on parts made of iron, steel, or allied materials.
Which of the following nondestructive tests can be used on parts made of conductive materials?
A) Liquid penetration testing
B) Magnetic particle testing
C) Eddy current testing
D) Radiographic testing
C = Eddy current testing
Eddy current testing applies an AC current through a coil near the surface of the part under inspection; therefore, only parts made of conducting material scan be tested with eddy current testing.
Which of the following organizations maintains the standards of measurement in the United States?
A) ISO
B) ASQ
C) NIST
D) SI
C = NIST
The National Institute of Standards and Technology (NIST) maintains the standards of measurement in the United States.
Which of the following is critical in metrology?
A) Physical artifacts
B) Paper standards
C) Definition of base units
D) All of the above
D = All of the above
All three of these areas must be taken into account in metrology. Physical artifacts must be manufactured with high precision (for example, gage blocks) in order to be used as masters for reference. Paper standards include the published documents that contain the specifications or accepted method for taking measurements. Definition of base units is critical as they form a reference from which all other units are derived.
How does NIST define the kilogram, the base unit of mass?
A) As a physical artifact used for direct reference
B) The amount of water required to fill a 36-ounce beaker
C) Based on the weight of carbon molecules
D) None of the above
A = As a physical artifact used for direct reference
The kilogram is the only base unit that is defined in terms of a physical artifact, which is made of a platinum-iridium ally and protected by the International Bureau of Weights and Measures in Paris. A duplicate is also protected by NIST in the United States.
Slight changes in temperature where parts are measured for conformance could lead to:
A) Systematic error in measurement
B) random error in measurement
C) operator error in measurement
D) type II error in measurement
B = random error in measurement
Errors in measurement are classified as random errors (accidental fluctuations that can not be predicted) or systematic errors (for example, operator error or calibration error). Ambient changes like slight temperature changes in a laboratory are classified as random error.
True/False: The most sensitive measuring equipment always leads to the most precise measurements.
A) True
B) False
B = False
Sensitivity is associated with the equipment and is defined as the least perceptible change in dimension detected by the measuring tool and shown by the indicator. Precision is associated with the actual measuring process; therefore, the most sensitive instrument may not always lead to the most precise results
To quantify a laboratory’s measurements system to national standards, a company would use which of the following?
A) Measurement assurance
B) Calibration
C) Traceability
D) Gage R&R study
C = Traceability
Traceability is intended to quantify a laboratory’s measurement uncertainty compared to national standards.
Information on the contribution to error of technicians or a laboratory’s procedures can typically be found in:
A) Measurement calibration records
B) Measurement traceability protocols
C) the material review board
D) measurement assurance protocols
D = measurement assurance protocols
Measurement assurance protocols provide details on the accuracy of a measuring instrument as well as the contribution to measurement error of technicians, the laboratory environment, and a laboratory’s procedures.
The goal of equipment calibration is to maintain the system’s:
A) accuracy
B) precision
C) sensitivity
D) readability
A = accuracy
The aim of calibration is to maintain a measuring system’s accuracy
While analyzing repeated measurements of a quality characteristic, an employee notices that the values are consistently larger than the reference value. Which of the following has occurred in this measurement process?
A) Random error
B) Systematic error
C) Type I error
D) Type II error
B = Systematic error
In measurement system analysis, there are tow types of errors: systematic error and random error. Systematic error can be caused by humans, imprecise measuring devices, or poor manufacturing methods. It will remain relatively constant over repeated measurements. Random error is inherent fluctuations in the measuring system. Type I and type II errors are found in hypothesis testing (type I error occurs when a true null hypothesis is rejected; type II error occurs when a false null hypothesis is not rejected).
Which of the following components of a measurement system contributes to its accuracy?
A) Repeatability
B) Reproducibility
C) Linearity
D) Random error
C = Linearity
The accuracy of a measurement system consists of gage bias, linearity, and stability. Repeatability and reproducibility describe the precision of the measurement system
Which of the following does not contribute to variability in measurement system error>
A) Correlation
B) Linearity
C) Bias
D) Reproducibility
A = Correlation
Measurement system error variability can be attributed to gage bias, stability, linearity, repeatability, reproducibility, and accuracy. Correlation measures the linear relationship between two quantitative variables.
The length of a part should be 6.00 cm. A particular part is repeatedly measured six times, yielding the following measurements:
6.05, 5.94, 5.98, 6.01, 6.03, 5.97
What is the resulting bias for this part?
A) 0.003
B) 5.997
C) -0.003
D) 0.041
C = 5.997
Bias is defined as the observed average minus the reference value. In the example, the reference value is 6.00 cm. The observed average is:
= (6.05 + 5.94 + 5.98 + 6.01 + 6.03 + 5.97) / 6
= 5.997
The lengths of three parts have the following reference values:
3.00cm 6.00cm 12.00cm
Then repeated measurements were taken for each type of part. The observed averages of these three samples were:
2.998, 5.843, 12.275.
Which of the following statements is true?
A) There is evidence of nonlinearity in this measurement system
B) There is evidence of stability issues in this measurement system
C) The measurement system is not reproducible
D) The measurement system is not repeatable
A = There is evidence of nonlinearity in this measurement system
Consider the bias for each of the three types of parts.
Linearity measures how changes in the size of the part being measured affect the bias of the measurement system. In this example, the bias worsens as the length of the part increases, indicating evidence of the nonlinearity in the measurement system. Stability is a measure of how well the measurement system performs over time. Repeatability is the variability of the test instrument when used to measure the same part. Reproducibility is the variability due to different operators or setups of the measurement system measuring the same part.
The precision of a measurement system can be defined as:
A) the difference between the recorded measurement and the target value of a quality characteristic.
B) the variability present when the same part is measurement multiple times under the same conditions.
C) the ability to get the same degree of bias in a measurement over time.
D) the ability to get the same degree of bias in a measurement for parts of different sizes.
B = the variability present when the same part is measurement multiple times under the same conditions.
Precision is defined as the variability encountered when the same part is repeatedly measuring using the same measurement system under identical conditions. Precisions is made up of repeatability and reproducibility. Accuracy refers to the relationship between the results from a measurement system and the target or reference value.
In a gage R&R study, the variance associated with repeatability was found to be 0.8842 and the variance associated with reproducibility was found to be 0.2466.
What is the variance associated with measurement error?
A) 0.6376
B) 1.4369
C) 1.1308
D) Not enough information provided
C = 1.1308
Add repeatability and reproducibility for total.
The ANOVA table below displays the results of a gage R&R study where two operators measured five parts three times each using the same gage.
Source df SS MS F p
Part 4 44 11 12.69 0.015
Operator 1 0.033 0.033 0.04 0.854
Part x Operator 4 3.467 0.867 0.70 0.599
Error 20 24.667 1.233
Total 29 72.167
Using this full model, what is the measurement error variability?
A) 0.867
B) 0
C) 1.233
D) 1.828
C = 1.233
The variance components can be found as follows: Operators = 0 Part x Operator = 0 Parts = 1.828 Error = 1.233
Based on the results from the gage R&R study in the previous question, which of the following statements are true?
Source df SS MS F p
Part 4 44 11 12.69 0.015
Operator 1 0.033 0.033 0.04 0.854
Part x Operator 4 3.467 0.867 0.70 0.599
Error 20 24.667 1.233
Total 29 72.167
A) There is a significant interaction between parts and operators
B) More operator training is necessary in this process
C) This is a capable process
D) None of the above
D = None of the above
Based on the p-values from the ANOVA table, there is not a significant operator effect, indicating that the operators are performing well and no additional training is needed. Also from the ANOVA table, there is not a significant interaction between part and operator. However, by looking at the percentage contribution of the gage R&R variation to the total variability, we see that the variability associated with repeatability is quite large. This indicates that the gage is not capable and the process needs to be investigated to reduce the variation associated with repeatability.
Refer to the gage R&R study in question 69. Suppose that the upper and lower specification limits for the quality characteristic are 30 and 10, respectively. What is the precision-to-tolerance ratio for this process?
Source df SS MS F p
Part 4 44 11 12.69 0.015
Operator 1 0.033 0.033 0.04 0.854
Part x Operator 4 3.467 0.867 0.70 0.599
Error 20 24.667 1.233
Total 29 72.167
A) 0.333
B) 0.370
C) 0.406
D) 0.523
A = 0.333
A gage R&R study was performed for a process using 10 parts, two operators, and three replicates. The R-chart display information about the gage capability. What conclusions can be drawn from this control chart.
A) There are significant differences between operators
B) The operators are consistent in their use of the gage
C) The gage is not able to distinguish between parts
D) The gage is able to distinguish between parts.
B = The operators are consistent in their use of the gage
An R chart provides information about special causes of variation related to the gage R&R study. In this example, no points plot outside the control limits, indicating that the operators behave similarly and that there are no special causes of variation (for example, operator fatigue or operator training issues).
