CPS Process Measurement & Metrics 2 — Questions and Answers
Question 1: Takt time in process measurement is calculated as:
- Total production time divided by total units produced
- Available production time divided by customer demand rate (Correct answer)
- Cycle time minus wait time
- Number of defects divided by total units inspected
Correct answer: Available production time divided by customer demand rate
Takt time = Available production time / Customer demand, setting the pace at which a process must operate to meet demand without overproducing.
Question 2: The process capability index Cp measures:
- The ratio of the specification width to the natural process variation (6σ) (Correct answer)
- The percentage of products that meet customer requirements
- The number of standard deviations between the mean and the nearest specification limit
- The total cost of quality failures per production run
Correct answer: The ratio of the specification width to the natural process variation (6σ)
Cp = (USL − LSL) / 6σ, comparing the width of customer specifications to the spread of natural process variation to assess potential capability.
Question 3: First Pass Yield (FPY) is defined as the percentage of:
- Units produced within the scheduled time window
- Units that complete a process correctly without any rework or repair on the first attempt (Correct answer)
- Inspection points that pass without a defect being flagged
- Processes that meet their SLA on the first execution attempt
Correct answer: Units that complete a process correctly without any rework or repair on the first attempt
FPY measures the proportion of units that pass through the entire process correctly the first time, with no rework, scrap, or repair needed.
Question 4: In Statistical Process Control (SPC), control limits are set at:
- The upper and lower customer specification limits
- ±1 standard deviation from the process mean
- ±3 standard deviations from the process mean (Correct answer)
- The minimum and maximum values observed historically
Correct answer: ±3 standard deviations from the process mean
Control limits are placed at ±3σ from the process mean, representing the range of natural process variation; points outside indicate special-cause variation.
Question 5: Mean Time Between Failures (MTBF) is a metric used to measure:
- The average time it takes to repair equipment after a failure
- The average operating time between consecutive failures of a process or system (Correct answer)
- The frequency of scheduled preventive maintenance intervals
- The percentage of time equipment is available for production
Correct answer: The average operating time between consecutive failures of a process or system
MTBF quantifies the average duration of successful operation between failures, serving as a reliability indicator for equipment and processes.
Question 6: Cost of Poor Quality (COPQ) includes which of the following categories?
- Prevention costs and appraisal costs only
- Internal failure costs and external failure costs only
- Prevention, appraisal, internal failure, and external failure costs (Correct answer)
- Scrap costs and warranty claim costs only
Correct answer: Prevention, appraisal, internal failure, and external failure costs
COPQ encompasses all four cost-of-quality categories: prevention (avoiding defects), appraisal (inspecting for defects), and both internal and external failure costs.
Question 7: Defect rate as a process metric is most accurately expressed as:
- The number of defects found during final inspection
- The ratio of defective units to total units produced, often expressed as a percentage (Correct answer)
- The cost per defect divided by total production cost
- The number of customer complaints received per month
Correct answer: The ratio of defective units to total units produced, often expressed as a percentage
Defect rate = (Defective units / Total units produced) × 100%, providing a normalized measure of quality that allows comparison across different production volumes.
CPS Process Measurement & Metrics 2
Takt time in process measurement is calculated as: