Scrum knows only three different roles: the Product Owner, the Scrum Master and the development team.
The Product Owner owns and manages the Product Backlog. A PO is a single person who is alone accountable for the product.
The Scrum Master acts as a manager within the team and ensures that everyone is on the same page. He acts like a moderator in meetings and makes sure that the meetings only last as long as scheduled. The SM is also responsible for mentoring and teaching team members who need help to understand Scrum better. If there are any impediments for the development team, the SM ensures that these obstacles get removed. A good SM helps to increase the skills of the team which leads to a higher performance. Moreover, he also helps to implement Scrum within the company to guarantee an as effective process as possible. The SM does not make technical decisions.
The development consists only of developers. The team is self-organizing, which means that the team decides which and how Backlog Items will be implemented during the sprint. Usually, they take the top Backlog Items since these are prioritized the highest by the PO. The team members possess all the needed abilities to deliver a complete product at the end of the sprint.
The size of the team is somewhere between 3 and 9 developers. With less than 3 people Scrum doesn’t make much sense since there are no people working together who need to be managed. More than 10 developers bring too much complexity into the project to make progress. However, the PO and SM are not part of this count.
The Responsibility is shared between every team member. Since everyone is responsible for the product, sentences like “This is not my problem” should never come up. If there is a problem, it’s everyone’s problem.
For more information about the roles check out the documentation.
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