Team Size: What the Scrum Guide says vs. Others
From the scrum guide, the optimal development team size is 3 to 9 members. I have however read that the ideal team size is between 5 and 9. I am quoting the line I read from an online article.
the recommended Agile team size is 7 +/- 2. That means the ideal team size is between 5 and 9.
The reason for my post is because I was asked this question and I replied 3 to 9, and apparently I was wrong. The person asking me corrected me to state the above sentence. Now, what I'd like to understand is why does Scrum say 3 to 9? Is the answer for team size 7 +/- 2 correct? Where is this information coming from and perhaps the logic or science behind it? If it is correct, then why is the Scrum guide not being updated?
Just adding on to my post... I happened to read this in the meanwhile.
A quote from that article
By the time Hackman wrote the book “Leading Teams” his rule of thumb for team size was 6.
So, based on that if we say 6 +/- 3, then that would result in 3 to 9 (as per the scrum guide)
Therefore, which is correct and why?
The 7 +/- 2 guidance was advocated in the Scrum Primer and possibly other sources originating from trainers in the Scrum Alliance.
The Scrum Guide has advocated 6 +/- 3 and I understand that this is now accepted as being authoritative in both bodies. The primer has not been updated since 2012.
NB Another significant difference in the material, which you still encounter, is the idea of the PO being optional in a Sprint Retrospective.
The 7 +/- 2 guidance was advocated in the Scrum Primer and possibly other sources originating from trainers in the Scrum Alliance.
The Scrum Guide has advocated 6 +/- 3 and I understand that this is now accepted as being authoritative in both bodies. The primer has not been updated since 2012.
@Ian Mitchell, So can I safely say that the person who advocated that I correct myself is wrong? The defense from his end was that less than 5 people would prevent diversity in terms of knowledge, skills etc. If the right answer is 3 to 9, then how do I convince this person that he needs to update his knowledge.
If both answers are right, then I am not sure what is the right thing to be taught to those new to Scrum/Agile.
So can I safely say that the person who advocated that I correct myself is wrong? The defense from his end was that less than 5 people would prevent diversity in terms of knowledge, skills etc.
Less than 5 people could prevent diversity, depending on the situation. Scrum is as non-prescriptive as possible. 3 might be enough.
He is technically wrong, because his advice is contrary to the Scrum Guide. If he has expressed a desire to be technically right, perhaps in order to take a Scrum.org exam, you may therefore advise him accordingly. Otherwise I would consider the matter trivial since it is clear that such numbers are not meant to be an exact science, and reflect that perhaps Bezos got it right when he said “We try to create teams that are no larger than can be fed by two pizzas”.
Less than 5 people could prevent diversity, depending on the situation. Scrum is as non-prescriptive as possible. 3 might be enough.
He is technically wrong, because his advice is contrary to the Scrum Guide. If he has expressed a desire to be technically right, perhaps in order to take a Scrum.org exam, you may therefore advise him accordingly. Otherwise I would consider the matter trivial since it is clear that such numbers are not meant to be an exact science, and reflect that perhaps Bezos got it right when he said “We try to create teams that are no larger than can be fed by two pizzas”
Thanks @Ian Mitchell.
I just wanted to know the background of the two ranges, what needs to be taught in general and strictly when talking only about Scrum. It appears both answers are right but with one leaning towards the Scrum guide.
Here's what the Scrum Guide, circa 2009-2010 said about team size. It was 7, +/- 2 back then. I am unsure which version went to 3-9, the history page does not tell us.
The optimal size for a Team is seven people, plus or minus two. When there are fewer than five Team members, there is less interaction and as a result less productivity gain. What’s more, the Team may encounter skill constraints during parts of the Sprint and be unable to deliver a releasable piece of the product. If there are more than nine members, there is simply too much coordination required. Large Teams generate too much complexity for an empirical processs to manage. However, we have encountered some successful Teams that have exceeded the upper and lower bounds of this size range. The Product Owner and ScrumMaster roles are not included in this count unless they are also pigs.
@Chris Belknap, Thanks for that info. I am wondering if anyone knows why that revision took place to reflect 3 to 9.
I found this older post in these forums. It has a pretty good discussion on team sizes.
https://www.scrum.org/forum/scrum-forum/5759/development-team-size
Given that the post was done in 2014 and we know that in 2010 the recommendation was the 5 +- 2, then I draw the conclusion that the change occurred in the 2016 revision since it is the only revision after 2014 and prior that the only revision was in 2013, prior the posts creation.
I could be wrong but that is best I can do.