Backlog Estimation vs Backlog refinement
Backlog Estimation vs Backlog refinement:
when should PBI estimation(story point) takes place and when should backlog refinement (Grooming ) happens?
My understanding is PBI estimation should happen as soon as it is entered into PBI list along with priority.
who decides the size of PBI?
Have a read of Roman Pinchlers book Agile project Management with scrum (URL at bottom).
You will really have to get inside product owner role and the backlog if you are to become a true value optimizer. (To be fair all the books recommended for the PSPO help).
Estimation is part of Backlog Refinement. The Product Owner can add PBIs to the PB whenever he likes, they do not need to be estimated before. But he should take them to the next refinement to get them estimated regularly.
The people who can estimate the size best should decide about the size of a PBI. Usually these are the people who will do the work.
> My understanding is PBI estimation should happen as soon as it is entered into PBI list along with priority.
That's strictly correct, because a PBI must have a description, estimate, order, and value. If it lacks any of these attributes then it is not well formed.
> who decides the size of PBI?
In Scrum the Development Team are responsible for estimates. At scale, if a Development Team is not yet available then the best qualified people may provide initial estimates on a Product Backlog, but these will need to be redone once the team is assembled.