Schedule Network Analysis
For creating a final schedule, a schedule network analysis is completed using an initial schedule. Multiple techniques can be used to create the final schedule such as:
Critical path method
What-if scenario analysis
Critical chain method
A critical path is the longest path in a network diagram. The following steps are carried out in a critical path method: Longest path is determined through the network diagram Earliest and latest time when an activity can start is determined Earliest and latest date when an activity can be completed is also determined
A near-critical path is close in duration to the critical path. If the critical path and near-critical path are closer to each other in length, it increases the risk of the project. The project manager should focus on monitoring and controlling activities on both critical and near-critical paths to avoid any delays to project completion. FLOAT (SLACK) Floats are mainly of three different types:
Total Float (slack): The amount of time the activity can be delayed without delaying the project end date. Total float is considered as a primary type of float.
Free Float (slack): The amount of time the activity can be delayed without delaying the early start date of the successor(s)
Project Float (slack): The amount of time the activity can be delayed without delaying the externally imposed project completion date required by the management or by the customer. The float is an advantage for the project.
A float can be used by the project manager to:
Effectively manage the project
Achieve better allocation of resources
For example, if you have a new resource who is still learning and if you feel he will take longer to complete the task, you can allocate him to the activity which has maximum float. Thus, even if the activity is taking longer, it is less likely that the project will be delayed. The amount of float also indicates the time flexibility the project members may have for each activity. Formula for calculating float: Float = Late Start (LS) – Early Start (ES) Float = Late Finish (LF) – Early Finish (EF) Either formula will give the same result.
USING CRITICAL PATH METHOD
A forward and a backward pass need to be performed through the network diagram to determine the earliest and latest each activity can start and the earliest and latest each activity can finish. For the “early” figures, calculations are required from the beginning of the project to the end of the project, following the dependencies of the network diagram – a “forward” pass through the network diagram. For the “late” figures, calculations are required from the end of the project to the beginning, following the dependencies of the network diagram – a “backward” pass.
A few important points of critical path method include:
There can be multiple critical paths for a project
A project manager does not prefer to have multiple critical paths in a project as it increases risk
The critical path can change during the course of the project
If the float is negative, the project is behind schedule
The critical path has zero float
If the critical path has a negative float, corrective actions or changes are required to the project ?In case if the project has a negative float, the project manager should compress the schedule
The unrealistic time frame is one of the most common problems of any project. If the customer or stakeholders have requested for a date that cannot be met, or if the project has deviated considerably from the baseline, the project schedule requires compression. It is the responsibility of the project managers to push back, present options, and make sure the project is achievable by properly planning the project and using schedule network analysis techniques like schedule compression. The schedule compression technique helps in determining if the desired project completion date can be met and if not, what can be changed to meet the requested date. This can be done right at the project planning stage. This technique is also used during integrated change control to look at the impacts changes to other parts of the project (i.e. cost, scope, risk, resources, quality, etc) have on the schedule. The objective is to compress the schedule without changing the scope of the project.
This technique involves doing critical path activities in parallel that were originally planned in a series. Some of the disadvantages of fast-tracking are:
Results in rework
Requires more attention to communication
For example, using the network diagram shown here, which activity would you a fast track to shorten the project length. Assuming the dependencies are discretionary, activity H could be fast-tracked by making it occur at the same time, or in parallel with, activity G. Any other pair of activities on the critical path could be fast-tracked. Activities C and H could also be fast-tracked by having part of activity C done concurrently with activity H. CRASHING In crashing maintaining the project scope is important. This technique involves making cost and schedule trade-offs to determine how to compress the schedule the most for the least cost. Crashing always results in increased cost. It trades time with money.
WHAT-IF SCENARIO ANALYSIS
In creating a finalized, realistic schedule, it is helpful to ask “What if a particular factor changed on the project? Would that produce a shorter schedule?” The assumptions for each activity can change and, therefore, the activity durations can also change. One of the ways to calculate the effect of these changes is through a Monte Carlo Analysis.
MONTE CARLO ANALYSIS
The outcome of the project is simulated by computer software in the Monte Carlo analysis. It is based on the three-point estimate (optimistic, pessimistic, and most likely) for each activity and network diagram. Following are the benefits of the simulation:
It suggests the probability of completing the project on any specific day
It suggests the probability of completing the project for any specific amount of cost
It suggests the probability of any activity actually being on the critical path
It suggests the overall project risk
It is more accurate than other methods as it simulates the actual details of the project and calculates the probability.
Monte Carlo analysis help deal with “path convergence”, places in the network diagram where multiple paths converge into one or more activities, thus adding risk to the project. Monte Carlo analysis is also used as a risk management tool to quantitatively analyze risks.
A resource-limited schedule is produced using resource leveling. If resources are limited, leveling lengthens the schedule and increases the cost and other constraints.
CRITICAL CHAIN METHOD
Critical Chain method uses a network diagram and develops a schedule by assigning each activity to occur as late as possible to still meet the end date. You add resource dependencies to the schedule, and then calculate the critical chain. Starting at the end date, you build duration buffers into the chain at critical milestones. These reserves, spread throughout the project, will provide cushions for delays in the scheduled activities. You manage these buffers so that you meet each individual milestone date and thus the project milestone completion date as well.
The schedule can be shown with or without dependencies (logical relationships) and can be shown in any of the following formats, depending on the needs of the projects:
Bar chart (also called Gantt Chart)
Schedule control means looking for things that are causing changes and influencing the sources of the change. If the project can no longer meet the agreed-upon completion date (the schedule baseline), the project manager might recommend the termination of the project before any more company time is wasted. Bar charts are weak planning tools, but they are effective for progress reporting and control. They are not project management plans. Bar charts do not help organize the project as effectively as a WBS and a network diagram do. They are completed after the WBS and the network diagram in the project management process.
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