Schedule Analysis, Part 1: What is it?
A schedule is a time-model of how you as the supplier or manager plan on executing your project. It represents the project scope, resources, assumptions and constraints of the project. Like a cost model, the time model or schedule should respond to changes.
Schedule analysis generally evaluates two areas: schedule construction and schedule execution.
Schedule construction looks at how the schedule is built and whether it can provide predictable results based upon inputs or, in other words, is the schedule dynamic? That is, when the schedule is updated, will it change or respond to the given inputs.
Schedule execution looks at how the tracking or updates are entered, including whether there is a baseline against which to progress to measure. If there is no baseline, plan, or yard stick to measure against, then measuring performance is difficult at best.
You want to look at both schedule construction and schedule execution when performing schedule analysis. However, depending upon where you are in a project, you may tend to focus on one area. Projects that are being planned focus on schedule construction. Projects that are being implemented focus on schedule execution.
There are four generally accepted schedule development/analysis methodologies:
- The Defense Contract Management Agency (DCMA) 14 Point Assessment
- The General Accountability Office (GAO) Scheduling Best Practices
- The National Defense Industrial Association (NDIA) Planning and Scheduling Excellence Guide (PASEG)
- The Project Management Institute (PMI) Project Management Body of Knowledge (PMBOK)
Each part of schedule analysis has a slightly different focus, but they all look at both construction and execution. The reason being, even if you are only focused on execution, the foundation created during schedule construction can help or hinder schedule execution.
The GAO Scheduling Best Practices is the most comprehensive schedule analysis methodology since it was created to analyze schedules from programs undergoing a GAO audit. The GAO focuses on schedule construction, while DCMA focuses on schedule execution. GAO looks at four schedule characteristics:
A schedule is comprehensive if it reflects all activities in the program Work Breakdown Structure (WBS) or scope, not just those under contract. Programs get into trouble when they estimate the entire program, but only track the current work. Whether the schedule reflects all the resources (labor, materials, travel, facilities, and equipment) required to complete the work. Are the resources available or not? How long will each activity take to complete? The work should have specific start and finish dates, along with the ability to accurately and effectively measure progress as the work is being executed.
A schedule is well-constructed if all the activities are sequenced logically, and every activity except project start and project finish have both a predecessor and a successor. The schedule logic should be simple, such as Finish-to-Start (FS) dependencies. There should be a limited use of unusual or complicated logic. Unusual logic means anything other than FS, and Start-to-Finish relationships should not be used. Complicated logic is redundant logic, leads, lags, or constraints. Leads, lags and constraints should be documented and are frowned upon. Constraints limit the schedule’s dynamic ability. Leads and lags often hide work that is being done by someone else. An example of hidden work where a lag is often used is concrete cure time, or computer environment establishment. They both represent “work,” but are often left out of the schedule because the work is not done by the supplier. Redundant logic makes schedule analysis more difficult. An example of simple versus redundant logic is below.
The above example is simple logic. The schedule is “daisy-chained” together without redundant logic and it is a “closed” network. That is every activity except the start and finish have a predecessor and a successor. The predecessor of Activity B is Activity A. Activity A is preceded by Start.
The above logic is redundant. It is still a “closed” network, but the logic is more complicated than necessary. Activity B is preceded by Activity A. Activity A is preceded by Start. Including Start as a predecessor to Activity A is redundant logic. It only serves to make the schedule network unnecessarily complicated.
The critical path determines the activities that drive the schedule’s early completion date. This is simple Critical Path Method (CPM) scheduling.
Next, you want to ask if the critical path makes sense. Are the correct activities on the critical path, or does a management activity drive the critical path? Finally, a schedule is well-constructed when the total float reflects the schedule’s flexibility. In cases where there is high-float, more than 200 days, the schedule logic should be reviewed and potentially updated.
A schedule is credible if it is horizontally traceable. That is the work streams or sequences of activities lead to an outcome or deliverable. If the work doesn’t lead to an outcome or deliverable, then why is it being performed? Horizontal traceability is also concerned with having generally like work at the same level of the WBS. The schedule should be vertically traceability too. All scheduling applications do this out of the box except for Microsoft Project. Microsoft Project needs to have Manually Schedule changed to Auto Schedule. Vertical traceability means that the earliest start and latest finish of the children roll up to the parent early start and late finish. Vertical traceability includes having lower level events roll up to higher level events properly. If there are multiple schedules, the data between them needs to be consistent.
The schedule should contain some type of schedule margin or risk reserve for risks or uncertain events that may occur while the work is being completed. A schedule is also credible if it shows a project completion date with an associated confidence level. Having a confidence level indicates that some type of Monte Carlo simulation (MCS) or schedule risk analysis (SRA) has been performed. An SRA is a specialized skill set that is beyond most planners and schedulers. Risks are assigned to the schedule and a simulation is run, the results of which provides a range of completion dates and confidence levels. The problem with an SRA is that the results generally look the same, whether the schedule and its risks are comprehensive and well-constructed. The results can be a classic case of garbage in-garbage out while the results look good.
Now that the schedule has been developed, it is comprehensive, well-constructed, and will provide credible results, it can enter execution. During execution, the schedule must be controlled. By controlled, the schedule needs to be regularly updated by schedulers who are trained as schedulers. By regularly updated, the schedule should have progress entered monthly at a minimum. Schedule progress should have a status date in the schedule to determine schedule status as of date. The schedule should include actual progress completed and updated logic where required to determine forecast dates. A schedule narrative should accompany the schedule to describe updates and changes to the schedule since the last status date or delivery. Schedule status should be compared against a baseline to determine variances from the plan. The schedule should be subject to configuration control to determine what changes have been incorporated and when. Finally, a basis document should be included that defines the general schedule approach, assumptions, constraints and unique schedule features.
So, to summarize, schedule analysis generally looks at schedule construction and schedule execution. Schedule construction is important because it lays the foundation for schedule execution. Simply put, a house without a solid foundation will not withstand the test of time. Schedules are a dynamic time model that includes the entire scope, resources, assumptions and constraints of the project. The goal of schedule analysis is to create a schedule that is comprehensive and includes all of the project work. It should be well constructed and respond to inputs dynamically while representing the work as it is planned to be executed. It should be credible and include schedule contingency or schedule margin for those project risks that are realized. Finally, the schedule should be controlled so that inputs and changes are applied using a defined process that is consistently applied.
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