Critical Chain, Buffers & Schedule Risk
Probabilistic Project Scheduling: Shorter Lead Times, Fewer Missed Delivery Dates
Probabilistic scheduling predicts a range of outcomes instead of one date; aggregated critical chain buffers turn that into shorter project lead times.
Probabilistic project scheduling uses an understanding of variation in project tasks and the project environment (project risks) to make a quantitative prediction of a range of project outcomes. Instead of providing a fixed date to answer a question such as “When is first oil?” probabilistic scheduling provides a range of answers, such as “There is a 50% chance of achieving first oil by date x or sooner, and a 90% chance of achieving it by date y or sooner.”
A more general application of probabilistic planning also considers the range of project costs and returns. This article focuses on the range of outcomes for key project dates, such as first oil. Quantifying the range and probabilities of outcomes can aid project planning and decision-making.
Probabilistic scheduling provides a method to quantify the risk management process. Quantifying the impact of potential risks improves decision-making regarding the control of those risks and potentially the overall financial viability of the project. It specifically aids the upfront recognition of critical issues and the proactive management of those issues.
So how does better planning result in shorter project lead times?
First of all, there are fewer surprises. Having properly evaluated project risk and task durations, you’re prepared to handle the “Murphys” that always occur during project execution. Since you’ve already prepared, you can respond much more quickly, without wasting time.
Second, a good project plan moves these potential risk events off the critical path (if possible!). By moving risk events off the path that determines project delivery, you eliminate disruption to your deliveries. That doesn’t happen without planning.
Third, the tasks themselves are stripped of the safety that most project plans have, with all task safety aggregated at the end of the critical chain. Safety aggregation allows you to manage the safety as a project-level item, rather than letting it be dispersed to every resource in your project. That means you need less, and the overall project duration is shorter, with greater certainty of completing on time.
The short version is Projects in Less Time. The published books are on the Books page.