In the first half of sprint planning, the team asks questions of the Product Owner
to clarify what is to be built.

While estimating PBI size in Sprint Planning is technically allowed, it’s best to
estimate prior to planning.

The Product Owner assigns development tasks to the Team.

The Product Owner is involved in figuring out how code is written.

In the second half of Sprint Planning, the Product Owner may be needed to help
further clarify questions the team has.

The second half of Sprint Planning is for the team to break product backlog items
down into development tasks.

Development tasks can be sized in hours

A rule of thumb for sizing a task is that it should be between 4-16 hours of work.

Sprint planning for a 2 week sprint should be time boxed to 4 hours.

Adding a Backlog Refinement session half way through your sprint can help with
making the next Sprint Planning shorter and more effective.