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Network Analysis: The Best Practice for Calculating Duration

If you read my Guide to Network Analysis, made available last month, you hopefully gained a better understanding of a project’s “Network” and “Analysis.” The “Network” part being a logic diagram of connecting nodes (details of the individual tasks and the relationships between them), and the “Analysis” part describing the process of estimating the duration of each task and then calculating the timings for each task.

You may say that duration depends primarily on the quality of the resource doing the work, external factors like the weather, and so on. However, I believe the duration calculation needs a more hands on approach than that. A correct analysis of duration will act as the baseline for your project and providing you with an end date. It would be wise to generally restrict your deliberations to the time ONE resource will take to complete each task.

The only modifier you might have to use is for a task that, by its nature, will require two or more resources (or even a team). Refer to my example of carrying a long plank. If that is the case, base the duration calculation on one team’s effort. Again, I have a warning! Be aware that if you assign a team to do the work, then an individual resource within that team might have to be treated as a different resource for other tasks that may overlap.

The duration should be determined by the best qualified person using estimation techniques, previous knowledge, and/or even statistics! Try asking the resource that is going to do the task. You might get some interesting data!

I cannot stress enough the best practice of using a single resource duration, as that will end up giving you the best realistic figure for the end date. It will also allow you, in the future, to add additional resources reducing slippage of the overall time—time you would not have available otherwise.

Stay tuned! Next time, I’m planning to cover the forward and backward passes.

 

Mike Glen
Written by Mike Glen

Mike Glen from Oxfordshire, England is a Chartered Engineer and RAF pilot, who retired as a Wing Commander engineer after 32 years in the Royal Air Force. He spent eight years at Cranfield University at the Royal Military College of Science as a lecturer in project management and computer applications. Then, as a computer applications consultant for seven years, he specialized in training Microsoft Project. He was awarded MVP status in 1997 and has been re-awarded each year until 2011 (14 years). Now retired, apart from a continuing interest in computing, his spare time is taken up with four grandchildren, caravanning, visiting historic houses and gardens, serving as a lawn bowls club coach, Barbershop singing, and classical music. Mike is the co-author of Que: Special Edition Using Microsoft Project 2002 and contributor to TechTrax for Microsoft Project training. Connect with Mike as a contributor to the Microsoft Project User Group and Webmaster of the MVP Project web site at http://project.mvps.org.

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2 Comments
  1. I get the sense that in your article you are confusing LOE (Level Of Effort) with Duration. LOE is the amount of work to be done, Duration is how long will it take to complete that work (Duration = LOE/resources). I agree that when getting the estimate for the LOE it should be under standard work performance for that organization of either a single person or team, as appropriate. When I have the “true” amount of work to be done, then I can negotiate with resource managers for the appropriate amount of resources to meet the necessary Duration to satisfy the required completion date. Duration is what goes into the network diagram, but it is critical to first know the LOE, and the basis of that estimate. This is especially important when resources are trying to multi-task on one or multiple projects at the same time.

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  2. Good comment, Dirk! You are getting deeper into project planning than my the article was intended. For a beginner, let’s stick with a well estimated duration for one resource. When the newcomer gains experience, then he consider other ways of dealing with durations. Mike.

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