It is remarkable that a science which began with the consideration of games of chance should become the most important object of human knowledge — Pierre Simom Laplace, 1812.
The notion that all project variables are Random Variables is not well understood in many instances, especially in the agile community and those suggesting that estimating cost, schedule, and performance are not needed to make business decisions.
In some agile paradigms, fixed duration sprints mortgage the future by pushing unfinished or un-started features to future sprints resulting in a Minimal Viable Features outcome rather than the Needed Capabilities for the business case or mission success.
While possibly useful in some domains, many domains assume the minimum features are the same as the required features. Without all the required features, the system is non-functional. Management Reserve, schedule margin, and cost margin are needed to proetct those required features, their cost and their schedule from the random behaviours shown below.
When developing products or services using other peoples money, it is incumbent on us to have some understanding of how these random variables behave on their own and interact with each other. This knowledge provides the basis for making decisions about how that money will result in value to those providing the money. In the absence of that knowledge, those providing the money have no way of knowing when the project will complete, how much it will cost when it is complete, and what the probability is of the capabilities produced by the project to meet the needed business, technical, or mission goals. And most importantly how to make decisions based on those behaviours and interactions. They are deciding without the needed information of the consequences of their decisions.
To continue to assume otherwise ignores Laplaces.
