Probabilistic project scheduling uses knowledge of the 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 the question, “When will the project be completed?” probabilistic scheduling provides an answer with a range of certainty, i.e., “There is a 50% chance of project completion by date x or sooner, and a 90% chance of achieving it by date y or sooner.”
Project managers have known for centuries that accurately predicting a project's completion date is sometimes nothing more than an educated guess. Moreover, a project's end date is dictated as much by the business case as the actual work to be accomplished in the project. For a project owner, a primary consideration in project planning & control is to reduce project uncertainty.
Most projects, by their nature, are fraught with uncertainty. Often, projects are begun before the final design is complete. The complete design is not known and cannot be completed until the project is underway, so certain assumptions are made during project planning for: technology, site conditions, construction methods, resource availability, and more. Project managers are then forced to deal with “learning”
Probabilistic project scheduling recognizes and deals with the inherent uncertainty that exists in projects through a structured project planning & control process, then carries the application through a disciplined approach to project schedule management during execution.
Probabilistic Project Scheduling Benefits:
• Shorter Project Lead Times
• Improved credibility of the project plan
• Give a greater understanding of the work to be accomplished
• Consistent task estimates across groups
• Reliable task relationship linkages
• Greater assurance of risk and team focus
Improved control during execution:
•Earlier identification of problem areas
•More proactive project management
An additional application of probabilistic project planning & and control also considers the range of project costs and returns. This evaluation focused on the range of outcomes for key project dates. Quantifying the range and probability of outcomes supports accurate project planning and improved decision-making, improving the return on investment of the project.
Probabilistic project scheduling provides a method to quantify the risk event impact discovered during the risk management process. Quantifying the impact of potential risks improves decision-making affecting the control of those risks, and potentially on the overall financial viability of the project. It specifically aids the upfront recognition of critical issues and proactive management of those issues.
Buffer management (probabilistic project management) is the method used for project schedule management. When applied across multiple projects, it aids project and resource-level decision making to accelerate the completion of all of the projects sharing common resources.
Buffer management enables committing to high probability fixed dates while using the variation information provided by probabilistic scheduling and improves resource utilization and productivity by enabling resources to focus on project tasks in the correct sequence, completing them all sooner. Rather than switching back and forth between multiple tasks on multiple projects, resources can focus, recapturing the lost time previously devoted to setup and re-prioritization meetings. The focus of the entire project team is improved by rapidly identifying the project tasks requiring action (those with the most risk of causing delays) to ensure the project is finished on or before the committed project completion date.
Annette Hamilton, Director of Marketing