Hi I am currently in a Scrum Team where the Scrum Master and Product Owner exclusively decide which stories a team will work on for a sprint.
They are also exclusively responsible for analysing the accuracy of estimations and measuring velocity.
I am in favour of giving this responsibility to the team but I would like some unbiased opinions on the approach, pros/cons etc.
On
You sholud do it togehter as a Scrum Team. It's true that PO set business priorities but also there can be some technical blockers and dev team can support PO in that field. SM shouldn't make dacisions - his role is to support both, developers and PO to find best solution.
About velocity and estimations, that's is also part of SM work to help you identyfy your problems, ex with estimations and in general planing and analysing data helps here a lot to check if your estimations are ex too optymistic
I recommend a review of the scrum guide for a truly unbiased view. It's available from here : http://scrumguides.org/ The scrum guide is very clear on the separation of roles in the areas you've mentioned.
The product owner is responsible for the product backlog, including it's ordering.
The estimation of the items in the product backlog is the responsibility of the people doing the work (ie: the development team).
The selection for work to be taken in to a sprint is a collaboration between the product owner and the development team.
Velocity is a measure of the work completed in prior sprints. It doesn't need to be measured. It simply 'is'.