Activity Duration Estimating: Inputs

• Fast tracking. A schedule compression technique in which phases or activities that normally would be done in sequence are performed in parallel. An example would be to construct the foundation for a building before all the architectural drawings are complete. Fast tracking can result in rework and increased risk. This approach can require work to be performed without completed detailed information, such as engineering drawings. It results in trading cost for time, and increases the risk of achieving the shortened project schedule. .4 What-If Scenario Analysis This is an analysis of the question “What if the situation represented by scenario ‘X’ happens?” A schedule network analysis is performed using the schedule model to compute the different scenarios, such as delaying a major component delivery, extending specific engineering durations, or introducing external factors, such as a strike or a change in the permitting process. The outcome of the what-if scenario analysis can be used to assess the feasibility of the project schedule under adverse conditions, and in preparing contingency and response plans to overcome or mitigate the impact of unexpected situations. Simulation involves calculating multiple project durations with different sets of activity assumptions. The most common technique is Monte Carlo Analysis Section 11.4.2.2, in which a distribution of possible activity durations is defined for each schedule activity and used to calculate a distribution of possible outcomes for the total project. .5 Resource Leveling Resource leveling is a schedule network analysis technique applied to a schedule model that has already been analyzed by the critical path method. Resource leveling is used to address schedule activities that need to be performed to meet specified delivery dates, to address the situation where shared or critical required resources are only available at certain times or are only available in limited quantities, or to keep selected resource usage at a constant level during specific time periods of the project work. This resource usage leveling approach can cause the original critical path to change. A Guide to the Project Management Body of Knowledge PMBOK ® Guide Third Edition 146 2004 Project Management Institute, Four Campus Boulevard, Newtown Square, PA 19073-3299 USA The critical path method calculation Section 6.5.2.2 produces a preliminary early start schedule and late start schedule that can require more resources during certain time periods than are available, or can require changes in resource levels that are not manageable. Allocating scarce resources to critical path activities first can be used to develop a project schedule that reflects such constraints. Resource leveling often results in a projected duration for the project that is longer than the preliminary project schedule. This technique is sometimes called the resource- based method, especially when implemented using schedule optimization project management software. Resource reallocation from non-critical to critical activities is a common way to bring the project back on track, or as close as possible, to its originally intended overall duration. Utilization of extended hours, weekends, or multiple shifts for selected resources can also be considered using different resource calendars to reduce the durations of critical activities. Resource productivity increases are another way to shorten durations that have extended the preliminary project schedule. Different technologies or machinery, such as reuse of computer code, automatic welding, electric pipe cutters, and automated processes, can all have an impact on resource productivity. Some projects can have a finite and critical project resource. In this case, the resource is scheduled in reverse from the project ending date, which is known as reverse resource allocation scheduling, and may not result in an optimal project schedule. The resource leveling technique produces a resource-limited schedule, sometimes called a resource-constrained schedule, with scheduled start dates and scheduled finish dates. 6 .6 Critical Chain Method Critical chain is another schedule network analysis technique that modifies the project schedule to account for limited resources. Critical chain combines deterministic and probabilistic approaches. Initially, the project schedule network diagram is built using non-conservative estimates for activity durations within the schedule model, with required dependencies and defined constraints as inputs. The critical path is then calculated. After the critical path is identified, resource availability is entered and the resource-limited schedule result is determined. The resulting schedule often has an altered critical path. The critical chain method adds duration buffers that are non-work schedule activities to maintain focus on the planned activity durations. Once the buffer schedule activities are determined, the planned activities are scheduled to their latest possible planned start and finish dates. Consequently, in lieu of managing the total float of network paths, the critical chain method focuses on managing the buffer activity durations and the resources applied to planned schedule activities. A Guide to the Project Management Body of Knowledge PMBOK ® Guide Third Edition 2004 Project Management Institute, Four Campus Boulevard, Newtown Square, PA 19073-3299 USA 147