I attended an event hosted by Rally software in Boston 2 days back, which I honestly thought was very well organized and well run. One of the breakout sessions I attended in this event had close to 25 participants and one of the comments from that session really caught my attention.
One participant mentioned, "Our management is comparing Velocity of 2 teams, one in US (local) and one in Bangalore (offshore) and based on the velocity, they want to make a decision if the local work can be outsourced to a cheaper location". What made this even more interesting was that at least 30%, if not more, from the audience felt that velocity of the teams can be compared. Some mentioned that if team sizes are the same then comparison should be ok. And then there were others like me voicing our opinion, "Velocity between two teams CANNOT and should NOT be compared".
As far as I recall from Mike Cohn's book, and from my practice, my understanding is that velocity metric is a very 'team' specific metric. Velocity is a measure of how much work (# of Story Points) a team can accomplish in single iteration, and average velocity of a team is used for predicting how long (how many iterations) this team will take to finish their backlog.
Let's take a hypothetical example. There are 5 stories in the product backlog that both team A and team B are asked to work independently on. For this exercise, also consider that both teams are of same size and have equal expertise. Each team were given the numbers they could use to assign story points, "1,2,3,5,7,13,20”. Each team assigned story points to stories based on their understanding (as shown below). Each team also finished 5 stories in single iteration.
Team A calculated story points as
| Story 1 | 7 |
| Story 2 | 3 |
| Story 3 | 5 |
| Story 4 | 3 |
| Story 5 | 2 |
| Velocity | 20 |
Team B calculated story points as
| Story 1 | 7 |
| Story 2 | 7 |
| Story 3 | 5 |
| Story 4 | 7 |
| Story 5 | 3 |
| Velocity | 29 |
If one uses merely Velocity as a comparison metric, it gives a false impression that Team B is able to accomplish more than Team A, but that's not the case as both teams accomplished equal amount of work. If the management team used the above comparison to make a decision, they might choose wrongly.
Thoughts?
2 comments:
Interesting post Hiren!
I think the comparison of Velocity across teams is a dangerous approach. Velocity is a usefully metric that can help the team to understand if they are setting themselves up for success when planning the next iteration. The team doesn’t want to over commit or under commit when planning for the iteration and velocity can help here. Past performance can be a good benchmark.
While the scrum teams velocity may be of interest to others outside of the team, imo it shouldn’t be used for cross team comparison. I’d even go so far as to suggest that its likely to introduce problems, rather than solve any, or provide any meaningful comparisons between teams.
Kevin
Some interesting discussion on this article at
http://groups.yahoo.com/group/scrumdevelopment/message/41489
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