CAPM Predictive Plan-Based Methodologies Practice Question
A project manager is performing quality control on a batch of manufactured components. The team collects data on the number of defects per unit and wants to determine whether the process is stable over time and to identify any unusual patterns. Which tool should the project manager use?
⚠ Common exam trap
The trap here is selecting a quality tool that analyzes causes or priorities rather than one that monitors process stability over time.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Control chart
A control chart is the correct tool because it displays process data over time with statistically derived control limits, enabling the project manager to determine whether the process is stable and to identify special cause variation. The other tools serve different purposes: Pareto for prioritization, cause-and-effect for root cause analysis, and scatter for correlation between two variables. Only the control chart addresses time-based stability and pattern detection.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Pareto chart
Why it's wrong here
A Pareto chart is a histogram ordered by frequency that helps identify the most significant causes of defects. It is useful for prioritizing improvement efforts but does not show process stability over time or detect trends. The scenario requires monitoring process behavior across time to spot unusual patterns, which is beyond the Pareto chart's purpose.
- ✗
Scatter diagram
Why it's wrong here
A scatter diagram shows the relationship between two variables to test for correlation. While useful for identifying possible cause-and-effect relationships, it does not track a single process over time or indicate stability. The scenario involves monitoring defect counts across time to detect patterns, which is not the purpose of a scatter diagram.
- ✓
Control chart
Why this is correct
A control chart plots data over time with control limits to distinguish common cause variation from special cause variation. It reveals whether a process is stable and highlights unusual patterns such as trends or points outside limits. This directly matches the need to assess process stability and detect anomalies in defect counts.
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Cause-and-effect diagram
Why it's wrong here
A cause-and-effect diagram, also called a fishbone or Ishikawa diagram, organizes potential causes of a problem into categories. It is used for root cause analysis, not for monitoring process stability over time. The scenario asks for detecting unusual patterns in data collected over time, which requires a time-ordered plot rather than a causal diagram.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official PMI exam blueprint
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