Schedule Management

Estimating Activity Duration: A Key Aspect of Project Schedule Management

In the realm of project schedule management, the process of estimating activity durations holds a pivotal role. This process delves into estimating the count of work periods necessary to wrap up individual activities, given the estimated resources at hand. The output? A duration estimate for each activity, a vital cog in the wheel for crafting a realistic project schedule.

The inputs, tools, techniques, and outputs involved in the Estimate Activity Durations process are critical to its successful execution. These include the scope of work, required resource types or skill levels, estimated resource quantities, and resource calendars. The project team, particularly those most familiar with the specific activity, provide valuable inputs for duration estimates.

Several factors can influence duration estimates. These include constraints on the duration, effort involved, type of resources, and the schedule network analysis technique used. The duration estimate is progressively elaborated, considering the quality and availability of the input data. As more detailed and precise data about the project engineering and design work become available, the accuracy and quality of the duration estimates improve.

The number of resources and their skill proficiency can determine the activity's duration. However, changes to a driving resource allocated to the activity can affect the duration, but this relationship is not linear. The intrinsic nature of the work, such as constraints on duration, effort, or resources, can determine the time required to complete an activity, regardless of resource allocation.

The law of diminishing returns suggests that increasing one factor, such as resources, while keeping others fixed, will eventually yield smaller increases in output. Doubling the number of resources does not necessarily halve the time required, as it may increase duration due to risk, knowledge transfer, learning curve, additional coordination, and other factors.

Advances in technology can play a significant role in determining duration estimates, as they can increase output and impact duration and resource needs. The project manager also needs to consider the motivation of staff, including the tendency to procrastinate (Student Syndrome) and the tendency for work to expand to fill the time available (Parkinson's Law).

Every estimate of activity duration should come with a solid backing of documented data and assumptions. This documentation, far from being a mere formality, is a critical requirement for all data and assumptions feeding into the duration estimation. It serves as a beacon of transparency, fostering understanding and facilitating communication among the project's stakeholders.