Wednesday, 23 October 2013

Estimate Activity Durations

For the list of activities identified along with the list of identified resources for the concerned activities and based on the resouce calendars, what is the estimated time to complete each of the activities is what gets covered as part of Estimate Activity Durations process. Most of the times, the resource estimation, duration estimation is all done as part of project scheduling and it is also an iterative process considering the need to come up with a better schedule that befits client deadlines.

The Schedule Management Plan has details about how to come up with the duration estimates. The plan is a common input to all the processes within the concerned knowledge area since it provides direction and guidelines to tailor the different processes within the knowledge area.
Activity list contains the list of all activities identified for the project while Activity attributes has additional information like description or priority and so on.
In order to come up with the duration estimates, the key input is the no. of resources to work on the concerned activity. Understandably, based on the quantity and quality of the resource, the activity's duration would change. An experienced resource is better equipped with skills to complete the activity in a lesser duration compared to an inexperienced one.
Resource Calendars are nothing but identified resource's availability in the project timeline. Certain resources will be available only in the night shift. It also holds the vacation schedule for the concerned resource. The vacation schedule needs to be accounted when coming up with the activity duration.
While requirements usually cover aspects related to the project work as needed by the stakeholders, the project scope statement is more stringent in terms of specifying what is mandatory and what is not. Also, since the activity list is derived from the scope statement as the original source, the scope statement is looked up in order to be sure about any assumptions / constraints. Examples of constraints might include anything related to organizational constraints in terms of not having resources in the expected experience range.
Risk register covers the list of project risks. The risks might influence the duration of the activity. If a resource would be unavailable midway, then that will affect the activity duration as such.
The resource breakdown structure provides the hierarchy of available resource by category and type. This helps in understanding the available options in order to make a quick decision about the activity durations.
Enterprise Environment Factors is a vital input to this process plainly because this is a planning process since planning needs good understanding of environmental factors influencing the project and they need to be accounted.
Organizational Process Assets: Any formats or lessons learnt in similar projects in the past.

The tools and techniques used as part of this process are:
Expert Judgment: A vital tool during planning normally employed by SMEs.
Analogous Estimating: A technique wherein one project is estimated based on another due to the similarity and then the estimation accommodates for any differences by adding a buffer using expert judgement. This technique is used when there is very less details available about the project requirements. This is less time consuming and it has more risk too because due diligence is not used to come up with an accurate estimate.
Parametric Estimating: Based on what work a resource can do per time period, the time period to cover the activity is calculated and this is termed parametric estimation. This is normally used when there wouldn't be much change in the kind of work being done from time to time.
Three-point Estimating uses 3 possible estimates like optimistic, pessimistic and most likely values and extra-polates the values to come up with the estimate number. This needs good expert judgment else, this can become inaccurate or totally irrelevant to say the least. There are two types of calculations shown as below:
- Triangular Distribution. tE = (tO + tM + tP) / 3
- Beta Distribution (from the traditional PERT technique). tE = (tO + 4tM + tP) / 6
Group Decision Making Technique: In some scenarios where there is no proper data available to make an estimate, a group decision making approach based on available information is the best approach to follow. This uses techniques like braistorming, Delphi technique etc.
Reserve Analysis:Duration Estimates also involves estimation for contingencies or risks. There are different types of risks like Known Unknowns and Unknown Unknowns. These are accounted in the estimate as buffers. The different types of reserves are:
Contingency reserves are buffers for known unknowns for which mitigation plan is available. They are a percentage of the activity duration or a fixed work period might be added to account for them. The duration gets reduced as more clear visibility is available about the mitigation approach.
Another type of reserve is management reserve to account for unknown unknowns. They are not part of schedule baseline. So, use of the management reserve may include a change in the schedule baseline.

The outputs from this process are:
Activity Duration Estimates: What is the duration for the concerned activity based on different constraints like resource capability , resource calendar and so on. This estimate usually has a range to denote a rough order magnitude.
Project Document Updates: Project documents like activity attributes get updated as part of this process.


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