A new Scrum Master finds a recurring ninety-minute "refinement ceremony" in the calendar every Wednesday, mandatory for the whole Scrum Team, and is asked what its official timebox is and who is required to attend. What is the accurate answer?

Professional Scrum Master I, objective 3. Managing products with agility medium

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The options

Not correct Ninety minutes is close enough; the Guide gives refinement no more than ten per cent of the Developers' capacity

Wrong, and it is the most quoted number that is not in the 2020 Guide. That ten per cent figure comes from older material and no longer exists as a rule.

Not correct It is timeboxed like the other events, in proportion to the Sprint length, and the whole Scrum Team must attend

Wrong. Timeboxes belong to the events: Sprint Planning, the Sprint Review and the Sprint Retrospective each carry a maximum for a one-month Sprint, and the Guide adds only that for shorter Sprints the event is usually shorter — no proportional scale. Refinement is not on that list at all.

Correct Refinement is not an event, so it has no timebox and no prescribed attendance — a standing session is an optional way to do an ongoing activity

Correct. Scrum names five events, and refinement is not among them; it is an ongoing activity, so any regular slot is a team's own practice rather than a rule of the framework.

Not correct It is an event of the Sprint but an untimeboxed one, so it may run as long as the Product Owner needs

Wrong on both halves. Every Scrum event is timeboxed, which is part of why refinement's lack of a timebox is the clue that it is not one.

Why

The events exist to create regularity and to minimise the need for meetings not defined in Scrum, and refinement is deliberately left outside that set so a team can do it whenever the backlog needs it — in a session, in pairs, in ten minutes after a Daily Scrum. A standing meeting is fine. Calling it an event, giving it a mandatory attendance list, or defending it as required by Scrum is where teams go wrong.

Where this comes from

Cited
Scrum Guide section Product Backlog
What it says
This is an ongoing activity to add details, such as a description, order, and size.

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