PMP lesson · Scope & Requirements · Scope · lesson 2 of 3 · about 7 minutes
WBS and the scope baseline
Predictive · hybrid (agile uses the backlog instead)Free preview
Goal: After this lesson you can build a simple WBS, explain the 100% rule and the work package, and name the three parts of the scope baseline.
1The situation
Who owns the interlocks?
The robot cell plan has a line called “Guarding”. The guarding subcontractor installs the fence, then leaves. The electricians assumed the subcontractor would install the door interlocks and their wiring. The subcontractor assumed the electricians would.
Nobody did it. The interlocks were simply not inside anybody's box of work.
A good work breakdown structure prevents this: every piece of work is in exactly one box, and each box has a clear description.
2What a WBS is
A work breakdown structure breaks the total scope into smaller and smaller parts, organised by deliverables, until each part can be estimated, assigned and controlled.
Deliverable
Organise by results
Levels describe things produced (panel, software, safety system), not activities.
Work package
Lowest level
Small enough to estimate cost and time, assign one owner and track.
100% rule
Complete
The WBS contains all the work, and only the work, in scope.
Creating the WBS is called decomposition. The team that does the work helps create it.
3A WBS for the robot cell
Level 1: the product. Level 2: major deliverables. Lowest level: work packages.
4How it looks on the exam
Exam-style question 1. A subcontractor installed perimeter fencing but not the door interlocks, which the design team assumed were included in the 'Guarding' work package. Both interpretations are reasonable. What would have MOST likely prevented this?
A. A more detailed Gantt chart
B. A WBS dictionary entry defining the content and boundaries of the work package
C. A larger contingency reserve
D. More frequent site meetings
Show the answer and the decode
Answer: B.
In simple English
Two parties understood one work package differently.
What is the question really asking?
What would have prevented the gap.
Key words / trigger
“assumed were included in the 'Guarding' work package”
PMP logic
The WBS dictionary defines exactly what each work package contains and where its boundaries are.
Why the wrong answer looks attractive
A Gantt chart shows timing, not the content of the work.
5Remember this
Your memory card
WBS = all deliverables and work, decomposed to work packages