An agile team is known by its capability to plan as a team. The team commits to a certain amount of features to be realized within a certain amount of time.
They often use historical data to determine how much they are capable of finishing on average, by using an average team velocity. This means that they have agreed that any team member can do any task. See also: generalizing specialists. Using the power of averages, this is often very accurate and easier to plan than using actual time based estimates.
Now what happens when the holidays come up? Suddenly half of your team could be unavailable.
An easy way to cope with this is to recalculate you velocity based on the relative completeness of your team.
Ex. The next four weeks, 2 team members are not available and 1 is only available for 2 weeks. 3 others are present full time. The team works in sprints of 4 weeks, with an average velocity of 25. How do we know the amount of features we can commit to as a team?
Well, take the iteration velocity and multiply it by the number of available team members divided by the total amount of team members.
This means that for the next iteration, we can only commit to 14,5.
The benefit of doing it this way is that we can still take a commitment as an entire team, with a velocity of the entire team for an entire sprint. It emphasizes the importance of a group working together towards a shared goal for a shared period.
For those who can forget about velocity and team commitment for a while, I wish you all a happy holiday!
(image by eyesogreen)