Self-organization is an essential management principle of Scrum. Yet, its importance and potential are only seeping through slowly. Despite the wide adoption of Scrum.
The most basic form of self-organization in Scrum holds that Development Teams organize and manage their own work within a Sprint, autonomously, against a forecast and a Sprint Goal. Where acceptance of this practice grows, few organisations take it a step further. Few teams are supported to figure out their own team size in order to best collaborate towards the creation of a releasable Increment of product in a Sprint. Understanding that the foundations for great work are commitment and motivation, Development Teams should be able to also create and re-create their structure and composition across time.
Collaboration is key. From collaboration performance emerges. Teams have the highest cohesion, the deepest trust and the most effective interconnections when the size of the team is around seven. Scrum used to have the rule known as 7 +/- 2, meaning a Development Team was expected to have at least 5 people, and 9 at most. The Scrum Guide has evolved this guidance to 3-9 people. This is confusing when looking for academic exactness, less confusing if this is seen as guidance against the goal of being “small enough to remain nimble and large enough to complete significant work within a Sprint“ (quote from the Scrum Guide).
Although the Scrum Guide sets an expectation for the size of a Development Team, there’s no formal process needed to really enforce this if self-organization is enacted. Through self-organization a team will adjust its size autonomously for optimal performance. Rather than instructing a team on their mandatory size, help a team discover what works best for them, including what team size maximizes the communication bandwidth. No external body can do this better. No external body can assess the combined effects of team dynamics, being co-located or not, availability of people and resources (tools, infrastructure), and all other parameters better than the people actually doing the work.
Try something you believe might work for you. Inspect it, adapt to your findings. Repeat. When heavily constrained in doing this, sticking to the guidance of having 3-9 people in a Development Team is a good idea.
In Scrum, actually… team size is a team decision.