The Rules of Scrum: PBIs have their effort estimated collectively by the team who will be implementing them

The Product Owner brings Product Backlog Items to the Scrum Team to estimate their effort (cost).  In order to create the right environment of safety and accountability, no Product Backlog Item is estimated by a single member of the Scrum Team, or even a subset of the team membership.  By having all the members of the Scrum Team participate in the estimation work for every Product Backlog item, it becomes impossible to blame a single Team Member for a poor estimate.  At a practical level, it is should be very rare that a single Product Backlog Item is fully implemented by a single Team Member.  Therefore, estimates should consider the collective effort of the Scrum Team, and this can only be determined by having all the Team Members participate in the estimation work.  If the team delegates estimation to a single person, or if one person dominates the estimation work, the other Team Members will not have ownership of the estimates and will be able to deny accountability.  The pressure on the team from collective estimation encourages teamwork, cross-training and these behaviours in turn promote the development of a high-performance team.

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2 thoughts on “The Rules of Scrum: PBIs have their effort estimated collectively by the team who will be implementing them”

  1. Seems like “Scrum Team” is used inappropriately a couple of times in this article. The “Scrum Team” is comprised of the Product Owner, ScrumMaster, and (development) Team. While the Product Owner relates information regarding the Product Backlog Items (PBIs), neither the Product Owner or the ScrumMaster should participate in the estimation (unless they are also (development) Team members, which while sometimes is the case is usually suboptimal).

    I also question whether this should be included in Scrum Rules. I don’t believe Scrum mandates that estimation must be done at all. Indeed some of the people who were instrumental in the development and promotion of Agile Estimation techniques now see them as having potential to be detrimental instead of useful. See:

    1. Hi Vernon! Thanks for the feedback. This is a tough one. First, I know about the “estimation is evil” arguments, and I do encourage teams to avoid estimation. However, there is _always_ some kind of estimation required for two things: choosing what to do in a Sprint and ordering the Product Backlog. These estimates might be informal, non-numerical, but they occur regardless. As for the Product Owner and ScrumMaster participating in the estimation of effort, again, I strongly encourage this behaviour, but since the Product Owner needs to provide information about the PBIs and the ScrumMaster needs to be aware of obstacles related to PBIs, it is impossible to fully separate them from the estimation work as well. Finally, the collective commitment to the work of a Sprint, release, project or product must be at the level of the Scrum Team, not the development team… which again means that the PO and SM have a stake in the estimates, are “pigs”, and therefore should at least have influence on how the estimates are determined. Disenfranchisement leads to lack of commitment which will prevent the creation of a high-performance Scrum Team.

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