In our blog, Deltek Acumen Risk and Activity Duration Uncertainty we discussed using Deltek Acumen Risk sliding bars feature for an efficient way to account for activity duration uncertainty in your schedule. In fact, it’s worth noting that many schedules don’t even account for duration uncertainty.
The Acumen Risk sliding bars provide an easy way to swiftly set up the uncertainty ranges of the durations and produce various what-if scenarios. If this was done manually, you would need a considerable amount of time to complete it.
However, if the intent during the development of a risk model is to make it as robust as possible, then the use of the Acumen Risk sliding bars capability for defining the durations uncertainty may not be the best option. However, if you have a particular groups of tasks, it may be fine.
One reason for this, is that the real parameters that cause the duration of a task to vary, cannot be reflected through the positioning of the sliding bar on one of its available places.
The resultant duration range can only coincidentally match the one an analytical and more rigorous process would produce. So, setting up the duration ranges via the sliding bars for the entire project would adversely affect the realism of the risk model. This would then affect the reliability of the results produced.
Specifically talking about construction projects, the tasks can be separated in the following typical groups.
- Design (Optional)
- Testing & Commissioning
The activities, of which the progress can be measured against the physical work being achieved, are the Construction tasks comprising approximately 50% – 70% of the tasks in a detailed schedule. These are exactly the tasks the duration uncertainty should be defined in an analytical way. The parameters affecting the minimum and maximum values of a duration range are as follows:
- Production Rate which is further dependent upon:
- The size of the crew – How many workers / pieces of equipment the assumed crew consists of.
- The skillfulness of the crew (e.g. Not all pipe fitters can install the same number of pipes within a day).
- Spatial parameters – whether or not a crew works at the same place along with other crews.
- Quantity (e.g. the uncertainty as to how many cubic meters will be finally excavated which can either prolong or reduce the initially estimated duration of the excavation activities).
So, if all the aforementioned parameters are put into the equation, the calculated duration range will be quite different than the one produced through the sliding bars in Acumen Risk. Given the number of the construction tasks in a schedule, it’s evident that the results of the simulation when an analytical approach is adopted, cannot be the same with the ones being produced with the easiness and ambiguity of the Acumen Risk sliding bars.
Nevertheless, the Acumen Risk sliding bars are useful. Particularly, when the duration range of activities belonging to the other groups of tasks need to be defined.
One example of this would be, the delivery time of the long-lead items that can decisively affect the timely completion of a project. These can be set by placing the sliding index on one of the available positions of the bar that is essentially linked to a pre-defined uncertainty pattern, set up by the analyst.