Rationale and Remedies
ADVISORY
By Dr. Kenneth Smith, PMP
Honolulu, Hawaii
& Manila, The Philippines
September’s article on Redundancy Theory[1] highlighted the use of reserve personnel and concurrent competitive activities to heighten the probability of completing high risk activities in a timely manner. This month I want to highlight a corollary concern: a frequently neglected step in critical path activity time computations — especially for merge milestones – which results in underestimating a project’s planned duration; thereby contributing to subsequent significant schedule slippages. So here’s the procedure & two templates to help you rectify the situation.
Almost all activity durations in projects are ‘ceiling estimates’ based on analogous experiences in other situations, sector ‘rules-of-thumb,’ or simply wishful thinking.
A wide variety of estimating techniques are also employed – the most ubiquitous of which is probably the pseudo-scientific PERT formula which computes a te — an ‘earliest expected time’ – for an activity, with a 50% probability based on three (3) time estimates;
Optimistic,
Most likely, &
Pessimistic
But you shouldn’t stop there.
When assigning time durations for critical path scheduling, the probabilities of the related activities are also significant; but all too frequently overlooked!
This is the shortcoming I want to highlight, and help you resolve.
First, to calculate ‘realistic times’ — or any other activity range of times with related probabilities — I developed the template in Figure 1 – on the following page — using an Estimated Standard Deviation (ESD), on which the PERT formula is based.
Figure 1
To illustrate the importance of probability on scheduling, the series of critical path activities in Figure 2 – on the following page — totals 13 days.
Since the probability of each activity is 90%, the probability for the 13-day path being completed on schedule is likewise 90%. Hence – while not always feasible — including a buffer of 1.4 days for the path[2] – rounded to 2 days — would improve the probability of success to a ‘realistic’ level.
More…
To read entire article, click here
How to cite this article: Smith, K. F. (2024). Schedule Slippages, Merge Milestones & Probability Theory: Rationale and Remedies, PM World Journal, Vol. XIII, Issue X, October/November. Available online at https://pmworldlibrary.net/wp-content/uploads/2024/11/pmwj146-OctNov2024-Smith-Schedule-Slippages-Merge-Milestones-Probability-Theory-1.pdf
About the Author
Dr. Kenneth Smith
Honolulu, Hawaii
& Manila, The Philippines
Initially a US Civil Service Management Intern, then a management analyst & systems specialist with the US Defense Department, Ken subsequently had a career as a senior foreign service officer — management & evaluation specialist, project manager, and in-house facilitator/trainer — with the US Agency for International Development (USAID). Ken assisted host country governments in many countries to plan, monitor and evaluate projects in various technical sectors; working ‘hands-on’ with their officers as well as other USAID personnel, contractors and NGOs. Intermittently, he was also a team leader &/or team member to conduct project, program & and country-level portfolio analyses and evaluations.
Concurrently, Ken had an active dual career as Air Force ready-reservist in Asia (Japan, Korea, Vietnam, Indonesia, Philippines) as well as the Washington D.C. area; was Chairman of a Congressional Services Academy Advisory Board (SAAB); and had additional duties as an Air Force Academy Liaison Officer. He retired as a ‘bird’ colonel.
After retirement from USAID, Ken was a project management consultant for ADB, the World Bank, UNDP and USAID.
He earned his DPA (Doctor of Public Administration) from the George Mason University (GMU) in Virginia, his MS from Massachusetts Institute of Technology (MIT Systems Analysis Fellow, Center for Advanced Engineering Study), and BA & MA degrees in Government & International Relations from the University of Connecticut (UCONN). A long-time member of the Project Management Institute (PMI) and IPMA-USA, Ken is a Certified Project Management Professional (PMP®) and a member of the PMI®-Honolulu and Philippines Chapters.
Ken’s book — Project Management PRAXIS (available from Amazon) — includes many innovative project management tools & techniques; and describes a “Toolkit” of related templates available directly from him at kenfsmith@aol.com on proof of purchase of PRAXIS.
To view other works by Ken Smith, visit his author showcase in the PM World Library at https://pmworldlibrary.net/authors/dr-kenneth-smith/
[1] Smith, K. F. (2024). REDUNDANCY IS GOOD! Say What? PM World Journal, Vol. XIII, Issue IX, September. https://pmworldlibrary.net/wp-content/uploads/2024/10/pmwj145-Sep2024-Smith-Redundancy-is-Good-Say-What-2.pdf
[2] i.e. 13 days / 90% equates to 14.4 days @ 100%; or a planned schedule shortfall of 1.4 days.
