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

The Developers size Product Backlog items, after clarifying them with the Product Owner. They are the ones doing the work, but they need the Product Owner’s input to understand what is being asked.

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 says “The Developers who will be doing the work are responsible for the sizing.” It continues that the Product Owner may influence the Developers by helping them understand and select trade-offs. Sizing is part of Product Backlog refinement, which the Scrum Team does together. That is why the answer includes the Product Owner’s clarification but keeps the final estimate with the Developers. People who do not do the work cannot give a reliable estimate, and people who do the work without understanding the item cannot either. The combination produces sizes the team can trust in Sprint Planning.

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 risks estimating the wrong thing.

C. The Product Owner with input from the Developers. This reverses ownership. The Product Owner informs the estimate, but the Developers make it.

D. Senior people such as architects and subject matter experts. People outside the Scrum Team do not size its work. Seniority does not replace the knowledge of those who will build it.

Exam Tip

Watch for the word “alone” in sizing questions. The Developers own the estimate, but Scrum.org questions often reward the option that includes collaboration with the Product Owner.

Key Takeaways

• The Developers who do the work size it.
• The Product Owner helps them understand items and trade-offs.
• Outsiders and managers do not estimate for the team.