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.
