What does the sentence "Refinement usually consumes no more than 10% of the capacity of the Development Team" mean in the Scrum Guide? How much effort is Product Backlog Refinement now?
Timeboxes of the Scrum events
The timebox for the Scrum events is relatively clear. Sprint planning: max. 2 h per week sprint; sprint review and sprint retrospective together also max. 2 h per week sprint; daily scrum max. 15 min. Hardly anyone has any questions.
But what is the timebox for the product backlog refinement?
Product Backlog Refinement is not an event
The first step to the answer is to understand that Product Backlog Refinement is not an event. Product Backlog Refinement is the entire work of the Scrum Team on the Product Backlog. Product Backlog Refinement can include some joint work time ("meetings"), e.g. an estimation with the team. But it also includes the work of the Product Owner at their desk.
With product backlog refinement, we therefore speak of effort - and not of a timebox as with events.
Effort, not timebox for product backlog refinement
But how much effort is involved? What exactly does the 10 % mean?
The larger the team, the more stories have to be completed sprint by sprint, and the more effort is required for product backlog refinement. The effort required for product backlog refinement therefore depends on the size of the team.
Let's calculate this briefly with an example: We have a team of 8 people and a sprint length of 10 days. The team capacity is therefore 80 person days (PT), the effort for the product backlog refinement is 10%, i.e. a maximum of 8 PT.
Who does the refinement?
How we distribute this effort is not specified in the Scrum Guide. There are many different solutions for managing this effort.
However, it is clear that the product owner (PO) and the development team do this work together. If the PO were to do the refinement alone, it would be the classic relay race approach. Sometimes we come across teams that do an "alternative scrum". They can be recognized by sentences like: "PO, this requirement is not good enough, we can't work with it like this, go back and come back when you're done." So: Refinement is a joint task - and consequently a joint effort by the PO and the development team.
The following refinement variants are possible, for example:
- The PO does a lot of refinement work and an estimation meeting with the development team. The distribution is then 1 PT or 8h for the 1h meeting with the team, and 7 PT for the PO alone. In this case, the PO is employed full-time, as in addition to the refinement, he also carries out the sprint acceptances (as well as sprint planning and sprint review).
- The product owner lets the team do a lot of the work. He comes to the development team with epics and has them detailed by the team. To do this, he meets with the team twice for 2 hours. Here, the team "consumes" 4 PT and the PO 4 PT. In this case, the PO still has time to take care of other tasks if necessary.
Conclusion
Product backlog refinement is ongoing work and as such has no timebox. That is why the Scrum Guide states: The effort for refinement is 10% of the team's capacity. Each team can decide for itself how these person-days of effort are distributed between the PO and the development team.
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