Probability and Impact Matrix: Threats and Opportunities Scoring

PMBOK v8 Definition

The Probability and Impact Matrix is a grid for mapping the probability of each risk occurrence and its impact on project objectives if that risk occurs. Risks are prioritized according to their potential implications for meeting project objectives, using a common matrix where opportunities and threats are represented using positive definitions of impact for opportunities and negative impact definitions for threats. Descriptive terms (such as very high, high, medium, low, and very low) or numeric values can be used for probability and impact, and these numeric values can be multiplied to give a probability–impact score for each risk, which allows the relative priority of individual risks to be evaluated within each priority level.

Why It Matters for the Exam

This concept appears frequently in PMI exam questions about risk prioritization and response planning. You will see it in situational questions where you must determine which risk needs immediate attention, and in definition questions asking you to distinguish between qualitative risk analysis tools. The matrix is the core tool for prioritizing risks before developing responses.

Key Points to Remember (for the exam)

• Probability Scales: Five levels are typical (Very Low 0.10, Low 0.30, Medium 0.50, High 0.70, Very High 0.90)
• Impact Scales for Threats: Negative impacts use values like 0.05, 0.09, 0.18, 0.36, 0.72 (Very Low to Very High)
• Impact Scales for Opportunities: Positive impacts use the same values but interpreted as benefits (reduced time/cost, performance enhancement)
• Score Calculation: Probability × Impact = Probability-Impact Score (e.g., High probability 0.70 × High threat impact 0.36 = 0.25 score)
• Common Matrix Structure: Threats are on the upper-left side (high probability, high negative impact), opportunities on the lower-right side (high probability, high positive impact)
• Three-Level vs Five-Level: Simpler processes use three levels; more detailed risk approaches typically use five levels
• Priority Levels: Scores determine risk priority within each level (Very High, High, Moderate, Low, Very Low)

Typical PMI Exam Example

A project manager identifies a risk that has a 70% probability of occurring and would cause a 36% delay in the project schedule. Using the Probability and Impact Matrix, what is the probability-impact score for this threat? Answer: 0.70 × 0.36 = 0.25. This score places the risk in the High priority level, requiring proactive response planning.

PMI Exam Traps

• Trap: Confusing probability values (0.90 = Very High) with impact values (0.72 = Very High)

  • Reality: Probability and impact use different numeric scales; probability reaches 0.90, impact reaches 0.72

• Trap: Using the same impact scale for threats and opportunities

  • Reality: Threats use negative impact definitions (delay, additional cost); opportunities use positive impact definitions (reduced time, performance enhancement)

• Trap: Assuming all risks fit neatly into the matrix

  • Reality: Some risks (ethical, reputation, team morale) may not map directly into probability and impact scales

• Trap: Multiplying descriptive terms instead of numeric values

  • Reality: Only numeric values can be multiplied; descriptive terms are used for categorization, not calculation

Important PMI Connections

Quick Review Questions

1. A risk has a probability of 0.30 and an impact of 0.36. What is the probability-impact score, and what priority level does it fall into?

2. What is the difference between using descriptive terms versus numeric values in the Probability and Impact Matrix?

3. A project uses a three-level risk approach. How many probability levels would typically be used compared to a five-level approach?

4. When evaluating an opportunity with a probability of 0.70 and a positive impact of 0.36, what does the score of 0.25 represent?

5. Which types of risks might not map directly into the probability and impact scales?

PMBOK v8 Reference

Section 4.2 - Probability and Impact Matrix (Table 4-2 and associated text)