Answering: “Who is responsible for the sizing of Product Backlog items?” (PSPO I)

The Developers size Product Backlog items, after clarifying them with the Product Owner. The Product Owner can explain and influence, but the people doing the work give the estimate.

Exam Question

Who is responsible for the sizing of Product Backlog items?
(choose the best answer)
A. The Scrum Master.
B. The Developers, alone.
C. The Product Owner with input from the Developers.
D. The most senior people in the organization, including architects and subject matter experts.
E. The Developers after clarifying requirements with the Product Owner.

Correct Answer

E. The Developers after clarifying requirements with the Product Owner.

Why This Is the Correct Answer

The Scrum Guide is direct on this point: “The Developers who will be doing the work are responsible for the sizing.” It then adds that “The Product Owner may influence the Developers by helping them understand and select trade-offs.” Sizing is part of Product Backlog refinement, which is a collaborative activity. The Developers need to understand what an item means and why it matters before they can judge its size, and that understanding comes from talking with the Product Owner. The best answer therefore combines Developer ownership of the estimate with Product Owner clarification.

Why the Other Options Are Wrong

A. The Scrum Master. The Scrum Master may facilitate refinement but does not size the work.

B. The Developers, alone. The Developers own the estimate, but sizing without the Product Owner’s clarification ignores the collaboration the Scrum Guide describes.

C. The Product Owner with input from the Developers. This reverses the accountability. The Product Owner gives input, the Developers decide the size.

D. Senior people such as architects and experts. People outside the team who will not do the work should not size it. Their estimates also reduce the team’s self-management.

Exam Tip

When two options name the Developers, pick the one that includes collaboration with the Product Owner. “Alone” is usually a trap word.

Key Takeaways

• The people doing the work size the work.
• The Product Owner clarifies and can influence trade-offs.
• Sizing happens during collaborative refinement.