Removing the Early-Dates Bias in CPM Risk Analysis

The Critical Path Method (CPM) schedules activities to start on early dates, which results in an unrealistic completion distribution in CPM risk analysis. CPM risk analysis tools, thus, cannot model what commonly occurs when a project unfolds and activities start on dates later than early dates due to floating or pacing decisions based on schedule progress. Graphical Path Method (GPM®) risk analysis allows activities in each realization to float as a function of random sampling and decision rules, accurately modeling the real world where activities are delayed to take advantage of total float.

This presentation demonstrated how the early bias in CPM risk analysis leads to optimistic completion distributions, and how GPM risk analysis corrects for the early bias by allowing floating and pacing scenarios. A novel approach was introduced for developing a bounding completion distribution envelope for selecting realistic probabilistic completion dates and for monitoring safe-float use as the project progresses.

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PRESENTED BY VIVEK PURI, PHD, PMP, EIT

Vivek PuriDr. Vivek Puri completed his bachelor’s degree from Punjab Engineering College in Chandigarh (India) and his master’s degree from Indian Institute of Technology Madras in Chennai (India). He then earned his doctoral degree in civil engineering from Purdue University, with a specialization in construction engineering and management. His doctoral work was in the area of simulation applications for construction planning. After his graduation, he joined PMA as a research engineer to identify, improve, and develop NetPoint and NetRisk.

COAUTHORED BY GUI PONCE DE LEON, PHD, PE, PMP, LEED AP

Dr. Gui Ponce de Leon is one of our nation’s foremost planning and scheduling experts. His professional experience includes roles as investor’s developer, construction manager, program manager, and EPC contractor planner/scheduler. Dr. Gui has continually pioneered innovations in project management throughout his 40-year career. With GPM, he is on a quest to transform scheduling from a task performed by specialists using a “black box” to stakeholder-centric processes that promote collaboration, enhance stakeholder interaction, and inherently result in reliable schedules.

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