Since the Scrum Team only includes three roles: ScrumMaster, Product Owner, and the Team Members, there is no need to have other people on the team. Each of the Scrum roles has a specific function that requires their full-time attention. These roles are all the roles necessary to accomplish the creation of a high-performance Scrum Team. Adding people to the team who have any other roles will hinder the team from engaging in the requisite amount of self-organizing behaviour.
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