What-If Analysis: Evaluating Scenarios for Schedule Impact

PMBOK v8 Definition

What-if analysis is the process of evaluating scenarios in order to predict their effect (positive or negative) on project objectives. This process answers the question: "What if the situation represented by scenario X happens?" A schedule network analysis is performed using the schedule to compute different scenarios, such as delaying a major component delivery, extending specific engineering durations, or introducing external factors like a strike or a change in the permit process. The outcome can be used to assess the feasibility of the project schedule under different conditions and in preparing schedule reserves and response plans to address the impact of unexpected situations. (This technique falls under the Schedule Management Knowledge Area, within the Develop Schedule process.)

Why It Matters for the Exam

What-if analysis is a frequently tested modeling technique on the PMI exam because it directly links schedule management with risk management. You will see this concept in questions about schedule reserves, contingency planning, and assessing schedule feasibility under uncertainty. Exam questions often ask you to distinguish what-if analysis from other schedule network analysis techniques like critical path method or resource optimization.

Key Points to Remember (for the exam)

• Core Purpose: Evaluates scenarios to predict effects (positive or negative) on project objectives
• Key Question: "What if the situation represented by scenario X happens?"
• Primary Technique Used: Schedule network analysis performed using the project schedule
• Example Scenarios Tested: Delaying major component delivery, extending engineering durations, introducing external factors (strike, permit changes)
• Main Outputs: Assessment of schedule feasibility under different conditions, preparation of schedule reserves, and development of response plans
• Common Confusion: What-if analysis is NOT the same as sensitivity analysis—what-if evaluates specific scenarios, while sensitivity analysis determines which individual risks have the most potential impact
• Key Relationship: Results feed directly into schedule reserve determination and risk response planning

Typical PMI Exam Example

A project manager is developing the schedule for a construction project. The team wants to understand the impact if a key supplier delays a major structural component delivery by three weeks. The project manager uses the project schedule to run different scenarios, including the delayed delivery and an alternative scenario where engineering durations are extended. This allows the team to assess schedule feasibility and determine appropriate schedule reserves.

PMI Exam Traps

• Trap: Confusing what-if analysis with sensitivity analysis

• Reality: What-if analysis evaluates specific "what if" scenarios using schedule network analysis; sensitivity analysis uses tornado diagrams to identify which individual risks have the most potential impact on outcomes

• Trap: Thinking what-if analysis only evaluates negative scenarios

• Reality: What-if analysis evaluates BOTH positive and negative effects on project objectives

• Trap: Believing what-if analysis is a standalone technique

• Reality: What-if analysis is performed within schedule network analysis, which is the overarching technique used to generate the project schedule model

• Trap: Assuming what-if analysis replaces schedule reserves

• Reality: What-if analysis helps in PREPARING schedule reserves, not replacing them

Important PMI Connections

Quick Review Questions

1. What specific question does what-if analysis answer?

2. What are three examples of scenarios that can be evaluated using what-if analysis?

3. How does what-if analysis differ from sensitivity analysis in terms of purpose and output?

4. What is the relationship between what-if analysis and schedule reserves?

5. What overarching technique is used to perform what-if analysis?

PMBOK v8 Reference

Section 6.5.2.4 - Schedule Network Analysis (Modeling Techniques: What-If Analysis)