Scrum, Sampling, and the 90 Percent Syndrome

Relying upon a long-standing prediction derived from one of Software Engineering’s most durable and respected software development models, we show that the primary methodological design decision shaping Scrum can be understood as a sampling-based solution to the 90% Syndrome -- a solution that exhibits exactly the characteristics predicted for such a solution. Aside from contributing credence to Scrum’s claim of improved predictability, this direct connection to the "normal science" software engineering of the 80’s and 90’s refutes the widely held assumption that Scrum (along with other Agile methods) represents a major paradigm shift or a "Kuhnian revolution" and thus requires some new "theory of agility". Instead, we argue, that Scrum should be viewed as solving the 90% Syndrome in a manner that affirms normal science, and that its sampling strategy constitutes the central methodological design choice, independently providing coherent justification for nearly every other Scrum-specific methodological design choice. We close with observations about the implications for future research and about the limitations of this work.