Who is accountable for estimating the effort to complete the Product Backlog items?

The Development Team is accountable for estimating the effort required to complete the Product Backlog items because they have the necessary expertise and insight into the technical aspects of the work. The Development Team possesses the skills and knowledge related to the tasks involved, making them best suited to assess how much effort is needed to implement each item. This estimation is typically done during planning sessions, where the team collaborates to reach a consensus on the effort involved in delivering each backlog item.

In Scrum, the Product Owner focuses on maximizing the value of the product and managing the Product Backlog, but they typically do not provide estimates. Their role involves prioritizing the items based on business value and stakeholder feedback. The Scrum Master acts as a facilitator and coach for both the Development Team and the Product Owner, ensuring that Scrum practices are followed, but they do not estimate work themselves. Stakeholders can provide valuable input regarding priorities and needs, but they are not involved in the estimation of the technical effort needed to complete the items in the backlog. Therefore, the Development Team's role in estimating efforts is essential to ensuring an accurate and realistic understanding of what can be achieved within a given Sprint.