PMI Quality Planning & Control Charts 2 — Questions and Answers
Question 1: On a control chart, a 'run' of 7 consecutive points on one side of the mean indicates what?
- Random variation within control limits
- A special cause requiring investigation (Correct answer)
- The process has improved permanently
- The sample size is too small
Correct answer: A special cause requiring investigation
Seven consecutive points on one side of the mean (Nelson Rule 2) signals a non-random pattern indicating a special cause of variation.
Question 2: Which quality planning tool translates customer needs into specific technical requirements using a matrix diagram?
- Affinity diagram
- Quality Function Deployment (QFD) (Correct answer)
- Failure Mode and Effect Analysis (FMEA)
- Benchmarking
Correct answer: Quality Function Deployment (QFD)
Quality Function Deployment (QFD) uses the 'House of Quality' matrix to systematically translate voice-of-customer needs into technical design requirements.
Question 3: A p-chart is used to monitor which type of quality characteristic?
- The average measurement of a continuous variable
- The proportion of defective units in a sample (Correct answer)
- The number of defects per unit
- The range of measurements between samples
Correct answer: The proportion of defective units in a sample
A p-chart (proportion chart) tracks the fraction or proportion of nonconforming (defective) items in successive samples of varying or fixed size.
Question 4: In the context of quality planning, what is the primary purpose of a process flowchart?
- To assign responsibility for defect correction
- To visualize process steps and identify potential quality failure points (Correct answer)
- To calculate the cost of quality for each process step
- To rank defects by frequency of occurrence
Correct answer: To visualize process steps and identify potential quality failure points
Process flowcharts map the sequence of process steps, enabling teams to identify where defects might occur and target quality control efforts accordingly.
Question 5: What does the Lower Control Limit (LCL) on a control chart represent?
- The minimum acceptable specification set by the customer
- Three standard deviations below the process mean (Correct answer)
- The lowest data point ever recorded
- The target value minus the tolerance
Correct answer: Three standard deviations below the process mean
The LCL is calculated as the process mean minus three standard deviations (3σ), below which a point signals a statistically unusual event.
Question 6: Which of the following best describes 'common cause' variation in a process?
- Variation caused by an identifiable, specific event
- Natural, inherent variation present in every stable process (Correct answer)
- Variation that always requires immediate corrective action
- Variation introduced by a new machine or operator
Correct answer: Natural, inherent variation present in every stable process
Common cause variation is the natural, random noise inherent in a stable process and can only be reduced by fundamentally changing the process itself.
Question 7: A project manager notices six consecutive points trending steadily upward on an X-bar control chart. What should they conclude?
- The process is in control because no point has exceeded the UCL
- A special cause is likely present and should be investigated (Correct answer)
- The UCL needs to be recalculated with a larger sample
- The trend is normal and no action is needed
Correct answer: A special cause is likely present and should be investigated
Six or more consecutive points trending in one direction is a non-random pattern (a run rule violation) indicating a special cause even if no point crosses a control limit.
PMI Quality Planning & Control Charts 2
On a control chart, a 'run' of 7 consecutive points on one side of the mean indicates what?