PMI Quality Planning & Control Charts 3 — Questions and Answers
Question 1: When using a c-chart, what is being measured?
- The proportion of defective items per sample
- The number of defects per inspection unit (Correct answer)
- The mean of continuous measurements per sample
- The range of defect counts across samples
Correct answer: The number of defects per inspection unit
A c-chart monitors the count of defects (nonconformities) per unit where the sample size is constant, following a Poisson distribution.
Question 2: In quality management, 'prevention costs' are best described as:
- Costs to evaluate whether products meet requirements
- Costs to avoid defects from occurring in the first place (Correct answer)
- Costs of reworking defective products found internally
- Costs associated with warranty claims from customers
Correct answer: Costs to avoid defects from occurring in the first place
Prevention costs include planning, training, and process improvement activities undertaken before production to avoid defects from ever occurring.
Question 3: What is the purpose of the 'Plan-Do-Check-Act' (PDCA) cycle in quality management?
- To document lessons learned at project closure
- To provide a structured framework for continuous process improvement (Correct answer)
- To assign accountability for quality failures
- To set the acceptable defect rate for a product
Correct answer: To provide a structured framework for continuous process improvement
The PDCA cycle (Deming Cycle) provides a repeating four-step iterative process for continuously improving products, processes, and services.
Question 4: A project team uses a scatter diagram to analyze two variables. What conclusion can be drawn if the data points form a tight upward-sloping line?
- One variable causes the other to change
- There is a strong positive correlation between the two variables (Correct answer)
- The process is in statistical control
- The sample size is insufficient for analysis
Correct answer: There is a strong positive correlation between the two variables
A tight upward-sloping scatter diagram indicates a strong positive correlation, meaning as one variable increases the other tends to increase — though correlation does not imply causation.
Question 5: Which PMI process group does 'Control Quality' belong to?
- Planning
- Executing
- Monitoring and Controlling (Correct answer)
- Closing
Correct answer: Monitoring and Controlling
Control Quality is part of the Monitoring and Controlling process group and focuses on measuring actual results against quality standards.
Question 6: What is the key difference between 'quality planning' and 'quality assurance' in PMI's framework?
- Quality planning sets standards; quality assurance inspects finished products
- Quality planning identifies standards; quality assurance audits processes to ensure standards are followed (Correct answer)
- Quality planning is done once; quality assurance is done only at project closure
- Quality planning requires customer input; quality assurance does not
Correct answer: Quality planning identifies standards; quality assurance audits processes to ensure standards are followed
Quality planning identifies relevant quality standards and determines how to satisfy them, while quality assurance audits project processes to confirm standards are being properly applied.
Question 7: An R-chart (range chart) is used alongside an X-bar chart primarily to monitor:
- The central tendency of the process over time
- The variability or dispersion within each sample subgroup (Correct answer)
- The proportion of defects in each sample
- The cumulative sum of deviations from the target
Correct answer: The variability or dispersion within each sample subgroup
The R-chart monitors within-subgroup variability (spread), while the X-bar chart tracks the process mean, together providing a complete picture of process stability.
PMI Quality Planning & Control Charts 3
When using a c-chart, what is being measured?