One agile practice that goes directly to scope control (different from creep) and business value retention is the retrospective practice which engages the power of examination after the fact, or post-iteration (sprint) evaluation.
In systems speak, you are sampling the performance and by feedback to the team for the next iteration, you are affecting the next performance by affecting the scope going forward.
In Bayesian speak, you are updating the a priori estimate based on new observations and facts, and perhaps new estimates (I'll not say guesses!)
A bit of system engineering:
This is a classic feedback loop (the iteration is the object in the loop). Outcomes influence errors sources such that future errors are corrected or acknowledged.
The power of retrospective examination, however, is diluted if feedback is not phased properly. That is, the feedback must be timely such that a corrective action in practices and the composition of the backlog can be affected in time to make a difference.
I've often said that the difference between noise and song is only a matter of phasing.
Thus, is the scope is to be changed, the change must be viewed in a total context and not a context that is out of sync or out of sequence. This is what I mean by scope control as different from scope creep. Retrospective examination can help with the timing, particularly at scale when there are multiple retro's going on at nearly the same time.
Oops! Here comes the traditional guys:
Of course, there is a bit of irony here: traditional methods, once underway, are highly retrospective in their management practices. PMs are constantly looking back at actuals (cost and schedule) and earned value (scope accomplishment).
The glass half empty:
The problem with retrospective examination, if there is one, is the tendency to forecast forward based on a projection of the past into the future. That may be ok, but if any factors have changed, or will change, the past-is-the-future paradigm breaks down.
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