Your Agile Team: Too Big or Too Small?

Most Agile and Scrum training courses refer to a 7 +/- 2 rule, that is, agile or Scrum teams should be 5 to 9 members. Scrum enthusiasts may recall that the Scrum guide says Scrum teams should not be less than 3 or more than 9. Where does this thumb rule come from? and Why?

A study done by Lawrence H. Putnam and Ware Myers in 1998 investigated team size. Their findings were published in the Cutter Consortium in 1998. Putnam and Myers looked at 491 medium-sized projects, those with between 35,000 and 95,000 “new or modified” source lines of code. All were information systems and were completed between 1995 and 1998 (the last three years prior to publishing).

What Putnam and Myers confirmed was not only that smaller teams of five to seven delivered in less time but also that a significant increase in effort occurred when team sizes reached nine or more.

What Other People said?

According to the a post published in Wharton University of Pennsylvania website:

Should the most productive team have 4.6 team members, as suggested in a recent article on “How to Build a Great Team” in Fortune magazine? What about naming five or six individuals to each team, which is the number of MBA students chosen each year by Wharton for its 144 separate learning teams?

Is it true that larger teams simply break down, reflecting a tendency towards “social loafing” and loss of coordination? Or is there simply no magic team number, a recognition of the fact that the best number of people is driven by the team’s task and by the roles each person plays?

Summary

Scrum guide recommends that development team size should be between 3 and 9. The 7 ± 2 magic rule — came from a psychology paper called “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information” where it demonstrates that there are limits to how much information we can keep in our heads.

When working with team consultants, the right team size should be four to six core team members, allowing you to add between one and three consultants while still keeping the team sized correctly. Remember, consultants will come and go, but the core team should remain the same.