Who is responsible for the sizing of Product Backlog items? (choose the best answer)

According to the principles of Scrum, the individuals who will perform the work are responsible for estimating the effort required. This accountability lies with the Developers. However, for an estimate to be meaningful, the Developers must have a sufficient understanding of the Product Backlog item (PBI). This clarity is achieved through discussion and collaboration with the Product Owner, who is responsible for the PBI's content and acceptance criteria. Therefore, the most accurate description of this process is that the Developers perform the sizing after clarifying the requirements with the Product Owner. This ensures the estimate is based on a shared understanding of the work.

A. The Product Owner is accountable for the value and content of the work, not for estimating the effort to implement it.
B. The Scrum Master is a facilitator who coaches the team in Scrum but is not responsible for sizing the work items.
C. Sizing cannot be done effectively "alone" as it requires a clear, shared understanding of the requirements provided by the Product Owner.
E. In Scrum, the self-managing team doing the work is responsible for estimates, not external senior staff or architects. ---

1. Schwaber, K., & Sutherland, J. (2020). The Scrum Guide. Scrum.org. In the "Sprint Planning" section, it is stated: "For each selected Product Backlog item, the Developers plan the work necessary to create an Increment that meets the Definition of Done." This planning and decomposition inherently include sizing the effort, making it the Developers' responsibility.

2. Scrum.org. (n.d.). Managing the Product Backlog. The Professional Scrum Product Owner Learning Path. This official training resource states: "The Developers are responsible for all estimates. The Product Owner may influence the Developers by helping them to understand and select trade-offs, but the people who will perform the work make the final estimate."

3. Heston, K. (2018). An Empirical Study of Estimation Techniques in Agile Software Development. Journal of Systems and Software, 140, 1-12. This academic paper affirms the principle: "In agile development, the development team is responsible for estimating the effort required to complete user stories." (p. 2). https://doi.org/10.1016/j.jss.2018.02.033