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ICBB practice questions

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Question 1Define

In the context of ICBB process improvement work, what is the primary purpose of the Define phase?

  1. To statistically validate measurement system capability across the full process
  2. To run designed experiments that identify significant factor interactions
  3. To control the improved process using control charts and response plans
  4. To establish the project charter, scope, and customer requirements before improvement work begins Correct answer.

Explanation

The Define phase establishes why the project exists, what is in and out of scope, who the customer is, and what the team must deliver. Statistical validation, experimentation, and control all occur in later phases, so they cannot be the purpose of Define.

Question 2Define

A Six Sigma project charter contains a statement reading: "Reduce invoice processing cycle time from 12 days to 5 days within nine months." Which charter element does this statement represent?

  1. Goal statement Correct answer.
  2. Business case
  3. Problem statement
  4. Team roster

Explanation

A goal statement expresses the measurable target and timeframe the team commits to, including the metric, the baseline, the target, and the deadline. A problem statement instead describes the current undesirable condition without prescribing the target.

Question 3Define

A team writes a problem statement as "Our department needs better software because everyone is frustrated." Which weakness most directly disqualifies this as a usable Define-phase problem statement?

  1. It names a solution too early in the project lifecycle
  2. It fails to identify the executive sponsor of the project
  3. It lacks a measurable gap, baseline data, and a defined scope Correct answer.
  4. It does not include a completion date for the project

Explanation

A sound problem statement quantifies the current condition, states the gap against a standard or expectation, and bounds where and when the problem occurs. This statement offers only an opinion and a vague remedy, so it cannot be measured or scoped.

Question 4Define

Which pair of statements correctly distinguishes a project's scope from its boundaries in a charter?

  1. Scope lists the metrics; boundaries list the sponsors
  2. Scope defines what the project will address; boundaries state what is explicitly excluded Correct answer.
  3. Scope names the team; boundaries name the customer
  4. Scope sets the budget; boundaries set the timeline

Explanation

Scope clarifies the process, product, or area the team will investigate and improve, while boundaries and exclusions protect the team from expansion into areas outside its authority. Together they prevent scope creep and set stakeholder expectations.

Question 5Define

A team is identifying customers for a hospital discharge process. Which description best fits an internal customer?

  1. The patient who receives discharge instructions at home
  2. The insurance payer who receives the final claim
  3. The regulator that audits discharge documentation annually
  4. The inpatient nursing unit that hands the patient off to the discharge lounge Correct answer.

Explanation

Internal customers are people or functions inside the organization who receive the output of an upstream process step. The nursing unit receiving the handoff sits within the same value stream, unlike external parties such as patients, payers, or regulators.

Question 6Define

Which tool is most appropriate for translating vague customer comments into specific, measurable, and prioritized requirements during Define?

  1. A control chart of complaint counts
  2. A Pareto chart of defect categories
  3. A run chart of process output over time
  4. A CTQ tree linking needs to measurable requirements Correct answer.

Explanation

A CTQ tree starts with a broad customer need and drills down into specific, measurable characteristics that the process must satisfy. The other tools analyze existing data rather than translate qualitative customer input into requirements.

Question 7Define

A project team collects customer feedback using a mailed survey that reaches only households with registered mailing addresses. Which Define-phase concern does this most directly raise?

  1. The sample's representativeness of the customer base Correct answer.
  2. The measurement system's repeatability
  3. The control limits of the response variable
  4. The process capability index

Explanation

Voice-of-customer data must reflect the full customer population, and a sampling frame limited to registered addresses systematically excludes some customers. Bias in who is sampled distorts the requirements the team defines.

Question 8Define

In SIPOC analysis, what does the "P" element represent?

  1. The process steps that transform inputs into outputs Correct answer.
  2. The products delivered to the final customer
  3. The performance metrics used to judge the process
  4. The people assigned to each process step

Explanation

SIPOC stands for Suppliers, Inputs, Process, Outputs, and Customers, where the Process element is a high-level sequence of the steps that convert inputs into outputs. It is deliberately kept at a summary level rather than a detailed flowchart.

Question 9Define

A team drafts a SIPOC for a purchase-order approval process but can only name the process steps, not the suppliers, inputs, outputs, or customers. What is the most significant consequence for the Define phase?

  1. The team cannot perform a gauge repeatability study
  2. The team lacks a shared understanding of process boundaries and the customer receiving the output Correct answer.
  3. The team cannot compute a baseline sigma level
  4. The team cannot select a control chart for the improved process

Explanation

SIPOC's value in Define is agreeing on where the process starts and stops and who consumes its output. Without suppliers, inputs, outputs, and customers, the team has no agreed boundary or customer linkage to anchor the charter.

Question 10Define

A project sponsor asks the team to define the process boundary for a customer complaint resolution process. Which choice best establishes that boundary?

  1. From the customer's first purchase through all future interactions
  2. From the call center's shift start to its shift end
  3. From the moment the complaint is received to the moment the customer is notified of resolution Correct answer.
  4. From the company's founding to the present complaint backlog

Explanation

A process boundary should be defined by clear start and stop events that mark the transformation the team controls. Using receipt of the complaint as the start and customer notification as the end gives an unambiguous, measurable scope.

Question 11Define

Which of the following best describes the role of a project champion in a Six Sigma Define phase?

  1. Removes organizational barriers and secures resources for the project Correct answer.
  2. Performs the day-to-day data collection and analysis for the team
  3. Audits the team's statistical methods for technical accuracy
  4. Documents the detailed process map at the work level

Explanation

The champion is a senior leader who sponsors the project, clears obstacles, and ensures resources and alignment with organizational strategy. The champion does not perform the technical analysis, which belongs to the belt leading the project.

Question 12Define

A Green Belt discovers that the process owner for the area being improved was never informed of the project. What is the most likely Define-phase risk?

  1. The design of experiments will lack replication
  2. The measurement system will fail a gauge R&R study
  3. The control chart will show special-cause variation
  4. The improvement may face resistance and fail to be sustained after the project closes Correct answer.

Explanation

Process owners are accountable for the process after the project ends, so their early involvement secures buy-in and ownership of the improved standard. Excluding them raises the risk that changes are rejected or abandoned once the team disbands.

Question 13Define

Which statement about the business case within a project charter is most accurate?

  1. It records the names of all team members and their availability
  2. It explains the financial and strategic value of solving the problem to justify the investment Correct answer.
  3. It lists the process steps the team will map in detail
  4. It states the measurable target the team will achieve by the project's end

Explanation

The business case links the project to organizational strategy and quantifies the expected benefit, such as cost savings, revenue impact, or risk reduction. It answers why the organization should commit resources to this project.

Question 14Define

A team defines a defect as any invoice requiring more than one approval cycle. What characteristic must this definition have to be useful in the Define phase?

  1. It must be based on a statistical control limit calculated from past data
  2. It must include a root cause explanation for each occurrence
  3. It must be approved by an external regulatory body
  4. It must be agreed upon by the team and stakeholders and be measurable from existing or collectible data Correct answer.

Explanation

An operational definition translates a vague requirement into a specific, repeatable criterion that everyone applies consistently. It must be agreed upon and measurable, otherwise defect counts will vary by observer.

Question 15Define

Which element is typically found in a project charter but not in a problem statement?

  1. The identified sponsor and team with a project timeline Correct answer.
  2. A quantified baseline metric showing the gap
  3. Evidence that the problem exists in the process
  4. A description of the current undesirable performance gap

Explanation

The charter is the full project authorization document, so it includes roles, resources, milestones, and sponsor commitment in addition to the problem description. A problem statement is a narrower narrative of the gap itself.

Question 16Define

A team is scoping a project on late deliveries. Data show that 80% of late deliveries originate in the warehouse picking process, while 20% originate in carrier transit. The team has authority over warehouse operations only. Which scoping decision is most defensible?

  1. Limit scope to warehouse picking and document carrier transit as an exclusion Correct answer.
  2. Defer scoping until data on every carrier are collected
  3. Include carrier transit in scope because it contributes to late deliveries
  4. Expand the goal to eliminate all late deliveries regardless of source

Explanation

Scope should focus on the portion of the problem the team can control and improve, while explicitly excluding factors outside its authority. Documenting the exclusion keeps the charter honest and prevents later disputes about accountability.

Question 17Define

In a CTQ tree, a customer need of "fast service" is decomposed into which type of measurable requirement?

  1. A supplier qualification criterion
  2. A team meeting cadence
  3. A root cause hypothesis
  4. A specific performance measure such as average wait time in minutes Correct answer.

Explanation

A CTQ tree converts a broad need into measurable characteristics with units and targets that the process can be evaluated against. "Fast service" becomes something like wait time in minutes or time-to-response in hours.

Question 18Define

Which statement best describes the relationship between voice of the customer and critical-to-quality characteristics?

  1. VOC replaces the need for CTQs once customer interviews are complete
  2. CTQs and VOC are unrelated concepts used in different phases
  3. CTQs are derived from VOC and express customer needs as measurable process or product requirements Correct answer.
  4. VOC is derived from CTQs after the process capability is calculated

Explanation

VOC captures what customers want in their own language, and CTQs translate those wants into measurable specifications the process must meet. The flow runs from customer need to measurable requirement, not the reverse.

Question 19Define

A Define-phase team finds that two stakeholder groups define "on-time delivery" differently: one uses ship date, the other uses receipt date. What is the most appropriate action?

  1. Average the two definitions to satisfy both groups
  2. Create an operational definition specifying the exact measurement point and gain agreement Correct answer.
  3. Choose the definition used by the largest stakeholder group
  4. Postpone the project until the stakeholders resolve it independently

Explanation

Conflicting definitions must be resolved through an explicit operational definition that states exactly what is measured, where, and how. Agreement on that definition is essential so that baseline and improvement data mean the same thing to everyone.

Question 20Define

A charter review reveals that the goal statement reads "improve customer satisfaction significantly." What is the primary deficiency?

  1. It does not identify the project sponsor
  2. It omits the team's meeting schedule
  3. It fails to describe the process inputs
  4. It lacks a measurable metric, baseline, target, and timeframe Correct answer.

Explanation

A goal statement must be specific and measurable, typically stating the metric, the baseline value, the target value, and the deadline. "Significantly" cannot be evaluated, so the team cannot know when the goal is met.

Question 21Define

Which activity is most characteristic of the Define phase rather than the Measure phase?

  1. Establishing the project charter and validating the problem with stakeholders Correct answer.
  2. Conducting a gauge repeatability and reproducibility study
  3. Calculating baseline process capability indices
  4. Collecting data on defect rates over the past quarter

Explanation

Define is about authorization, scope, customer requirements, and team formation, which is where the charter and stakeholder validation belong. Measurement system studies, capability indices, and baseline data collection are Measure-phase activities.

Question 22Define

A team's process map shows that a customer service request passes through four departments, and each handoff adds a delay. In Define, what is the best use of this preliminary map?

  1. To prove statistically which department causes the delays
  2. To set control limits for the cycle time metric
  3. To compute the process sigma level for the baseline
  4. To identify the scope, key stakeholders, and potential areas of waste for the charter Correct answer.

Explanation

A high-level map in Define clarifies the process flow, who touches it, and where obvious delays or handoffs occur, informing scope and stakeholder analysis. It is descriptive, not a statistical proof of causation or capability.

Question 23Define

When building a high-level process map during Define, which level of detail is most appropriate?

  1. A summary of the major steps and handoffs sufficient to bound the process Correct answer.
  2. A full statistical model of each step's cycle time distribution
  3. A list of every individual transaction processed last year
  4. Every decision point and rework loop at the workstation level

Explanation

Define-phase mapping stays at a high level to establish boundaries, major steps, and handoffs without becoming lost in detail. Detailed flowcharts and data analysis come later once scope is agreed.

Question 24Define

A team identifies stakeholders for a billing improvement project. Which group is most likely to be a "process owner" rather than a "champion"?

  1. The Black Belt who facilitates the team's analysis
  2. The billing manager accountable for the process after the project ends Correct answer.
  3. The customer who receives the corrected invoice
  4. The vice president who funds the project and removes barriers

Explanation

The process owner is the manager accountable for the ongoing performance of the process and for sustaining improvements after the project closes. The champion provides sponsorship and resources, while the belt leads the technical work.

Question 25Define

A team claims its project will "reduce errors" but presents no data confirming the error rate or its impact. Which Define-phase principle is being violated?

  1. Projects must be led by an executive sponsor
  2. Projects must be completed within one month
  3. Projects should be based on a validated problem supported by data, not on assumption Correct answer.
  4. Projects must always include a design of experiments

Explanation

Define requires the team to validate that the problem is real, quantified, and worth solving before committing resources. Without baseline evidence, the project may address a perceived rather than actual problem.

Question 26Define

A Black Belt is drafting the problem statement for a Define-phase charter. Which wording best meets the criteria for an effective problem statement?

  1. Delivery performance is poor and customers are unhappy, so the team should improve it as soon as possible.
  2. Late deliveries are caused by the warehouse picking process, which must be fixed by the logistics team.
  3. Between January and March, 12% of shipped orders arrived later than the promised delivery date, versus a customer target of 2%. Correct answer.
  4. The company should reduce delivery delays because on-time delivery is a strategic priority for growth.

Explanation

An effective problem statement describes the observed gap using data, a time frame, and a comparison to a requirement, without asserting cause or prescribing a solution. Stating the measured gap (12% late versus a 2% target) keeps the Define phase focused on the problem rather than on a presumed remedy.

Question 27Define

In a Six Sigma project, which pair of elements establishes the measurable gap the project must close and the time frame in which it must be closed?

  1. Business case and team roster
  2. Voice of the customer and communication plan
  3. Problem statement and goal statement Correct answer.
  4. SIPOC diagram and Gantt chart

Explanation

The problem statement documents the current performance gap with data, while the goal statement specifies the target performance and the deadline for achieving it. Together they define the measurable improvement the charter authorizes.

Question 28Define

A team is writing a goal statement for a project on invoice processing errors. Which goal statement is most appropriate for a Define-phase charter?

  1. Eliminate all invoice errors by redesigning the accounts payable system.
  2. Investigate why invoice errors occur and address the underlying causes.
  3. Reduce invoice error rate from 8% to 2% by the end of the fourth quarter. Correct answer.
  4. Improve invoice accuracy so that the finance department is satisfied.

Explanation

A goal statement should be specific, measurable, attainable, relevant, and time-bound, and it should state both the baseline and the target. Reducing the error rate from a measured 8% to 2% by a stated quarter satisfies those criteria.

Question 29Define

A project charter is being reviewed before approval. Which element is essential to include because it authorizes the team to commit resources and cross functional boundaries?

  1. A complete list of potential root causes
  2. The sponsor's signature and authority statement Correct answer.
  3. A detailed statistical analysis plan
  4. A finished control plan for the improved process

Explanation

The charter is the document that formally authorizes the project, and sponsor approval conveys the authority needed to allocate resources and work across departments. Without that authorization, the team has no mandate to act.

Question 30Define

During a Define review, a Belt notes that the charter lists a project scope of "all customer-facing operations worldwide." What is the most significant risk of this scope?

  1. The team may need to recruit additional members from other regions.
  2. The project may require more frequent sponsor meetings.
  3. The scope may be too broad to complete within available time and resources. Correct answer.
  4. The charter may need to be translated into multiple languages.

Explanation

A scope that spans every customer-facing operation worldwide is typically too large for a single Six Sigma project to complete within its resource and time constraints. Narrowing scope to a manageable process boundary is a core Define-phase responsibility.

Question 31Define

A Belt is constructing a stakeholder analysis for a process improvement project. Which characteristic should be used to classify each stakeholder?

  1. Their seniority in the organization and their years of service
  2. Their geographic location and preferred working hours
  3. Their level of influence over the project and their degree of interest in its outcome Correct answer.
  4. Their functional job title and educational background

Explanation

Stakeholder analysis typically maps each party by influence (power to affect the project) and interest (stake in the outcome), which guides how to engage them. Seniority, location, and title alone do not indicate how a stakeholder should be managed.

Question 32Define

A Define team is selecting members for a project on reducing medication dispensing errors. Which set of roles best reflects a complete Six Sigma team structure?

  1. The chief executive, the chief financial officer, and an external consultant
  2. Only the Black Belt and a statistician, to keep the team small
  3. The entire pharmacy staff, so that everyone is informed at once
  4. A sponsor, a process owner, a Black or Green Belt leading the team, and subject matter experts from the process Correct answer.

Explanation

A balanced Six Sigma team includes a sponsor who provides authority and resources, the process owner who is accountable for the process, a trained Belt leading the improvement work, and subject matter experts who know the process in detail. This combination supplies mandate, accountability, method, and process knowledge.

Question 33Define

A project team is developing a charter and needs to record why the project is worth doing in financial and strategic terms. Which charter element serves this purpose?

  1. The milestone schedule
  2. The business case Correct answer.
  3. The team operating ground rules
  4. The communication plan

Explanation

The business case explains the strategic and financial justification for the project, including expected benefits and the cost of poor quality. It answers why the organization should invest resources in the effort.

Question 34Define

A Belt is defining the unit of analysis for a project on billing accuracy. Which statement correctly defines the unit being measured?

  1. The billing software version, because it determines how invoices are produced
  2. The accounts receivable department, because it owns the billing process
  3. The monthly billing cycle, because errors vary by month
  4. Each individual invoice issued to a customer, because it is the item that can be correct or defective Correct answer.

Explanation

The unit of analysis is the individual item that is evaluated as conforming or defective, which in this case is each invoice. Defining the unit precisely allows consistent counting of defects and opportunities.

Question 35Define

A team is preparing a high-level process map for the Define phase. Which convention is most appropriate for this map?

  1. Documenting the statistical distribution of each process output
  2. Depicting the major process steps and handoffs from supplier to customer Correct answer.
  3. Showing every decision diamond and rework loop in the process
  4. Listing each step in enough detail to write work instructions

Explanation

A high-level map created during Define shows the major steps and handoffs across the process, giving a shared view of scope without excessive detail. Detailed decision logic and work instructions come later in Measure and Improve.

Question 36Define

A project charter states that the team will reduce order-entry errors. The Belt notices the charter does not specify which departments, systems, or time period are included. Which Define-phase element is missing?

  1. The scope boundaries, including what is in and out of the project Correct answer.
  2. The control chart selection criteria
  3. The sampling plan for the measurement system study
  4. The hypothesis test to be applied

Explanation

Scope boundaries define what the project will and will not address, including the processes, locations, systems, and time frame covered. Without them the team cannot tell which data and improvements are within its mandate.

Question 37Define

A Belt is translating a customer requirement of "my loan application should be decided quickly" into a critical-to-quality characteristic. Which translation is most appropriate?

  1. The number of loan officers employed by the bank
  2. The total dollar value of loans approved each month
  3. The percentage of applicants who own their homes
  4. The average number of days from application submission to credit decision Correct answer.

Explanation

A CTQ characteristic must be a measurable performance attribute of the process that reflects the customer's requirement. Cycle time from submission to decision directly operationalizes the customer's desire for a fast decision.

Question 38Define

A Belt is documenting the voice of the customer for a Define-phase project. Which source provides the most direct and actionable input for identifying customer requirements?

  1. The company's organizational chart and reporting lines
  2. Historical financial statements from the prior fiscal year
  3. Internal opinions gathered informally in a team brainstorming session
  4. Structured interviews and surveys with customers who use the process output Correct answer.

Explanation

Direct, structured collection from customers who actually receive the process output yields specific and representative requirements. Informal internal opinion is subject to bias and does not reliably reflect customer needs.

Question 39Define

A Belt is building a Pareto chart of complaint reasons during the Define phase. The team must decide how to group the categories. Which approach best supports the project's purpose?

  1. Group complaints by the individual employee who handled each case
  2. Group complaints by the day of the week they were received
  3. Group complaints into a single category so that the chart is simple
  4. Group complaints by reason type so that the largest contributors to complaint volume are visible Correct answer.

Explanation

A Pareto chart ranks categories by frequency so the team can focus on the few causes that account for most of the problem. Grouping by complaint reason type makes the dominant contributors visible, which supports scoping and prioritization.

Question 40Define

A Belt must estimate the financial benefit that will justify a Define-phase project on scrap reduction. Which approach produces the most defensible estimate?

  1. Adopt the savings figure from a similar project described in a trade publication
  2. Use the largest scrap figure reported in any single month of the past year
  3. Ask the production supervisor for a rough guess of annual savings
  4. Multiply the targeted reduction in scrap units by the standard cost per unit, using validated baseline scrap data Correct answer.

Explanation

A defensible benefit estimate ties the targeted improvement to validated baseline data and a standard cost, so the calculation can be traced and audited. Financial representatives typically review such estimates before the charter is approved.

Question 41Measure

In a Six Sigma measurement system analysis, which property of a measurement system is defined as the closeness of repeated measurements by the same operator using the same instrument on the same part to each other?

  1. Reproducibility
  2. Stability
  3. Repeatability Correct answer.
  4. Linearity

Explanation

Repeatability captures the variation observed when one operator measures the same characteristic on the same unit repeatedly with the same gauge, so it reflects equipment and within-operator variation. Reproducibility instead reflects differences between operators or setups, while stability and linearity describe behavior over time and across the measurement range.

Question 42Measure

A gauge repeatability and reproducibility study reports %GRR of 9% of the study variation, and the process uses the gauge to sort parts against specification limits. What is the most appropriate interpretation?

  1. The study is invalid because %GRR below 10% cannot occur in practice.
  2. The measurement system is unacceptable and must be replaced before any decision.
  3. The measurement system is generally acceptable for this application. Correct answer.
  4. The gauge is acceptable only if the operators are retrained first.

Explanation

Common MSA guidelines treat %GRR below 10% as generally acceptable, 10% to 30% as conditionally acceptable depending on application, and above 30% as unacceptable. At 9% the system consumes a small share of the tolerance and study variation, so it supports the sorting decision.

Question 43Measure

Which measure of dispersion is most appropriate for describing the spread of a process characteristic when the analyst wants a statistic in the same units as the data and resistant to a few extreme outliers?

  1. Range
  2. Coefficient of variation
  3. Interquartile range Correct answer.
  4. Variance

Explanation

The interquartile range spans the middle 50% of observations, so it is expressed in the original units and is not driven by extreme values. Variance and range are both sensitive to outliers, and the coefficient of variation is a unitless ratio rather than a spread in data units.

Question 44Measure

A process produces parts whose measured diameters are normally distributed with mean 25.00 mm and standard deviation 0.10 mm. What proportion of parts is expected to fall above 25.20 mm?

  1. About 32%
  2. About 16%
  3. About 5.0%
  4. About 2.3% Correct answer.

Explanation

A value of 25.20 mm is two standard deviations above the mean, and the upper tail beyond z equal to 2 contains roughly 2.3% of a normal distribution. The other values correspond to different tail areas and do not match a two-sigma distance.

Question 45Measure

A control chart for individuals is being set up from 40 consecutive measurements. Which pair of charts is the standard companion set for this situation?

  1. p chart with an np chart
  2. X-bar chart with an R chart
  3. Individuals chart with a moving range chart Correct answer.
  4. CUSUM chart with an EWMA chart

Explanation

When subgroup size is one, short-term variation is estimated from the moving range between consecutive observations, so the I chart is paired with a moving range chart. X-bar and R charts require rational subgroups larger than one, and attribute charts apply to counted defectives rather than measured values.

Question 46Measure

On an X-bar and R chart, the R chart goes out of control while the X-bar chart remains in control. What is the correct interpretation and action?

  1. Both charts are in control because the X-bar chart shows no signal.
  2. The process mean has shifted, so the X-bar limits should be recalculated immediately.
  3. The within-subgroup variation is unstable, so the limits on the X-bar chart should not be trusted until the cause is found. Correct answer.
  4. The R chart signal can be ignored because range charts are less sensitive than X-bar charts.

Explanation

The R chart monitors within-subgroup spread, and its limits underpin the X-bar chart's control limits. An out-of-control range means the estimate of common-cause variation is unreliable, so assignable causes of variation must be investigated before interpreting or recomputing the X-bar chart.

Question 47Measure

A process has a specification of 10.0 plus or minus 0.5 mm, with process mean 10.1 mm and standard deviation 0.12 mm. What is the process capability index Cp?

  1. 1.67
  2. 1.11
  3. 1.39 Correct answer.
  4. 0.83

Explanation

Cp equals the specification width divided by six standard deviations, so 1.0 divided by 0.72 gives about 1.39. Cp ignores centering, which is why the separate Cpk would be lower for this off-center process.

Question 48Measure

A process is centered on target with Cp equal to 1.33. Approximately how many parts per million are expected to fall outside the specification limits, assuming normality and a stable process?

  1. About 63 ppm Correct answer.
  2. About 2700 ppm
  3. About 6 ppm
  4. About 233 ppm

Explanation

Cp of 1.33 places each specification limit four standard deviations from the mean. The two-sided normal tail beyond plus or minus four sigma is roughly 63 parts per million, which is the classic benchmark for that capability level.

Question 49Measure

Which statement correctly distinguishes Cpk from Ppk?

  1. Cpk applies only to attribute data while Ppk applies only to continuous data.
  2. Cpk and Ppk are identical whenever the process mean equals the target.
  3. Cpk uses overall variation while Ppk uses within-subgroup variation.
  4. Cpk uses within-subgroup variation while Ppk uses overall variation of all individual measurements. Correct answer.

Explanation

Cpk is computed with the within-subgroup standard deviation estimated from rational subgroups, whereas Ppk uses the overall sample standard deviation of all observations. When the process is in statistical control the two converge, but they differ when between-subgroup variation is present.

Question 50Measure

A Gage R&R study crosses three operators with ten parts, each measured twice. The average range method yields an equipment variation of 0.08 mm and an appraiser variation of 0.05 mm. What is the combined repeatability and reproducibility standard deviation?

  1. About 0.094 mm Correct answer.
  2. About 0.130 mm
  3. About 0.030 mm
  4. About 0.065 mm

Explanation

GRR standard deviation is the square root of the sum of the squared repeatability and reproducibility components, so the square root of 0.0064 plus 0.0025 gives about 0.094 mm. Combining standard deviations by simple addition would overstate the total.