Following on from comments to my post ‘Resourcing Schedules – A Conundrum’ there are still some basic problems to resolve.
As the commentators suggest, KISS is certainly an important aspect of effective resource planning: ie, planning resources at an appropriate level of detail for real management needs. But the basic issues remain; you cannot rely on a scheduling tool to optimise the duration of a resource levelled schedule.
No software I know of gets this one ‘right’.
When you play with the schedule, the answer to achieving the shortest overall duration is starting the critical resource (Resource 3) as soon as possible.
To achieve this Resource 2 has to focus 100% on completing Task B as quickly as possible BUT, Task C is on the Time Analysis critical path not Task B and 99% of the time software picks C to start before B.
This is not a new problem, a current paper by Kastor and Sirakoulis International Journal of Project Management, Vol 27, Issue 5 (July) p493 has the results of a series of tests – Primavera P6 achieved a duration of 709, Microsoft Project 744 and Open Workbench 863. Play with the resource leveling settings in P6 and its results are 709, 744, 823, 893 – a huge range of variation and the best option (P6) was still some 46% longer than the time analysis result . Other analysis reported in the 1970s and 80s showed similar variability of outcomes.
As Prof. George Box stated – All models are wrong, some are useful… the important question is how wrong does the model have to be before it is no longer be useful.
Computer driven resource schedules are never optimum, done well they are close enough to be useful (but this needs a good operator + a good tool). And good scheduling practice requires knowing when near enough is good enough so that you can use the insights and knowledge gained to get on with running the project. Remembering even the most perfectly balanced resource schedule will fall out of balance at the first update…..
How you encapsulate this in a guide to good scheduling practice is altogether a different question. I would certainly appreciate any additional feedback.