Can the Sprint length be changed once it has been established?
I know Another one of those third party mock test!!!
My answer was NO but I guess not!
A team should not change its sprint length back and forth. But that doesn't mean it's a life sentence. If the current length isn't working change it, but don't change every month. (Mike Cohn)
@Martin Premont, Yes, it can be changed, but not the length of the active Sprint.
Yes it can be changed, although predictability for workload, velocity etc will change, and needs to be accounted for.
Even the active sprint can be changed (altough I would advice against that); making it shorter might and likely will jeopardize reaching the sprint goal though, and lengthening it will most likely make the team drag in extra work which needs to be sprint ready.
Sprint lengths should be choosen to what fits the team cadence for a constant sustainable pace, keeping aligned on other organizational processes that might be in place. Therefore, choosing it and changing it must be done very carefully
A couple of quotes from the Scrum Guide section where the Scrum Events are introduced.
Once a Sprint begins, its duration is fixed and cannot be shortened or lengthened.
Sprints have consistent durations throughout a development effort.
Active Sprint duration should not change. That is the only limit I see as to changing the length. Based on my understanding of the definition of "consistent" it doesn't mean exact but it also doesn't mean always changing. Sprint duration should change if there is a valid reason for it to change but not just as a one-off change. If your team finds that 2 week sprints are consistently being too short to produce good increments of value, then they should consider different lengths. But as the Scrum Guide says
Sprints are limited to one calendar month. When a Sprint’s horizon is too long the definition of what is being built may change, complexity may rise, and risk may increase. Sprints enable predictability by ensuring inspection and adaptation of progress toward a Sprint Goal at least every calendar month. Sprints also limit risk to one calendar month of cost.
Find the cadence that works for the team to be able to produce increments of value long-term. The more you change the duration, the more difficult it will be for a team to start to realize their limits and establish a cadence.
Between Sprints, yes, but don't do this often. Make sure there is a good reason for the change. Forecasting becomes a lot more difficult when your historic data is of one Sprint length and your future Sprint lengths are another.