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How many people do you need in your team?

How big should your team be? It depends on what your goal is. In my classes, I have been showing the relationship between project size, cost and calendar time forever, based on research I had read, but could no longer find. Well, I think I have found the source, a 2005 paper from Team Size can be the Key to a Successful Software Project.

How big should your team be? Well it depends on what your most important goal is:
  1. If you are trying to keep costs down, a team size of 3 people or less is optimal.
  2. If you are trying to get a result as quickly as possible, a team size of 5 to 7 people is optimal.
  3. If you are trying to hit a budget or deadline as accurately as possible, again a team size of 5 to 7 people is optimal.
  4. If you are trying to burn a large budget, team sizes of 9 and up are best. These effects appear to be exponential.
Is item 4 really a goal? Nevermind. Silly question.

I think this data explains the Guidewire approach of keeping teams between 3 and 6 people. In effect, this has them cycling between lowest cost and fastest delivery, which is probably a sweet spot to find yourself in.

OTOH - This study is largely based on waterfall projects. Does anyone have the data to create a similar study of agile projects?


Comments

Hi Peter,

Great find! We've actually done (and continue to do) additional studies on team size, including completed agile projects, and the results have been surprisingly consistent. We also looked at team size best practices in our 2014 QSM Software Almanac: Research Edition. Hope this is helpful!

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