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PMP lesson · Project Initiation & Business Value · Starting the project · lesson 3 of 4 · about 6 minutes

Assumptions, constraints and competing demands

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Goal: After this lesson you can tell assumptions from constraints, manage them in the assumption log, and explain how the competing constraints affect each other.

1The situation

6 bar… or not?

The robot cell plan assumed that the customer's compressed air supply would be a stable 6 bar. Nobody measured it. During installation, measurements show 4.5–5.5 bar, fluctuating. The grippers fault.

At the same time, the customer insists the go-live date cannot move, the budget is fixed, and the line must meet a specific safety standard.

One of these was a belief that turned out false. The others are fixed limits. They need very different handling.

2Assumptions vs constraints

Every project starts with both:

Assumption
Believed true
Not proven. Must be verified and monitored. If false, it becomes a risk or an issue.
Constraint
A fixed limit
Date, budget, resources, regulations, contracts. Plan within it.
Assumption log
Where they live
Lists assumptions and constraints, owners, and status.
An assumption proven false → update the assumption log, assess the impact as a risk or issue, and agree actions with the responsible party.

3Competing constraints

ScopeTimeCostQuality also: risk · resources · benefits · customer satisfactionChange one side and the others are affected
The classic triangle, plus quality, risk, resources and benefits.

4How it looks on the exam

Exam-style question 1. The plan assumed the customer would provide 6 bar compressed air. Measurements during installation show 4.5 to 5.5 bar. The assumption is in the assumption log. What should the project manager do?
A. Ignore the measurements, since the assumption was agreed
B. Update the assumption log, assess the impact as an issue or risk, and agree corrective actions with the customer
C. Adjust the machines to 4.5 bar without telling the customer
D. Stop installation until 6 bar is available
Show the answer and the decode
Answer: B.
In simple English
An assumption proved false.
What is the question really asking?
The right handling.
Key words / trigger
“assumed … measurements … show”
PMP logic
False assumption → update the log, assess impact, agree actions with the responsible party.
Why the wrong answer looks attractive
Pointing to the agreement feels right, but the problem still must be solved.

5Remember this

Your memory card

  • Assumption = believed true → verify and monitor · Constraint = fixed limit → plan within
  • False assumption → update log, assess as risk/issue, agree actions
  • Competing constraints: scope, time, cost, quality, risk, resources, benefits
  • Make trade-offs transparent; change through governance
The full lesson in the PMCLEAR app also has:
  • the rest of the lesson (Competing constraints)
  • a worked example
  • the common traps (wrong vs right)
  • 2 exam-style questions with the decode
  • a 3-question quick check
Open the full lesson → Create a free account
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