What is a Project schedule?
A project schedule details the breakdown of a project’s activities and deliverables (and milestones) in terms of the time they will take. Preparing a schedule means knowing, firstly, what the work elements are (derived from the Statement of Scope and the Work Breakdown Structure). Then, for each activity, time estimates are derived, resources are allocated and any task dependencies identified.
A schedule, even if carefully prepared, is still a forecast beyond an actual point in time. To work, it needs the backing of those who input its data (e.g. resource requirements, time estimates, task dependencies). And it needs to be as accurate as possible. That is why, to work effectively, a project schedule must be constantly reviewed and updated.
Tools and techniques
Project Managers have access to a range of tools and techniques to develop and monitor project schedules. What these tools and techniques are, how they are used to monitor and review project schedules, is discussed in more detail in the ‘Scheduling tools and techniques’ topic in this unit. To recap, these include:
- GANTT Chart
- Schedule Network Analysis
- Critical Path Method
- schedule compression
- resource levelling and other resource monitoring
- risk multipliers.
Project review reports are very important in monitoring project schedules. These are typically prepared at key points during a project’s delivery:
- at project initiation, when the project’s business case is outlined and the parameters against which the project’s success will be measured are outlined
- when the project is planned, when technical and resource requirements are documented
- as the project is executed, by way of exception reports to management
- after the project is completed, when performance against pre-defined outcomes of time, cost and quality is assessed.
These reports provide another baseline against which schedule performance can be measured, enabling remedial action to be taken.
Earned value management as a performance measure
Another measure of project performance—and hence either an alert to potential problems or reassuring feedback about success—is the technique known as Earned Value Management (EVM). EVM works by quantitatively comparing work actually done with work planned.
- For example, one might think that a project one-third way through the schedule which has spent one-third of its budget might be on track. In reality, only about 10% of the work might have been completed. Or the converse might apply.
For EVN to work effectively, the work performance to be measured must include all work to be done. Each activity is assigned a planned value (PV) — which may be a measure of dollars spent or hours taken. The earning rules to be used are then determined. This may be: (i) no credit is given for an activity until it is 100% complete (the 0/100 rule), or (ii) the 50/50 rule, where half the credit is earned when the work begins, and half when finished. (Other rules, such as 80/20 rule, are variously skewed to getting the work started faster, or finished faster.)
As work progresses, the earned value (EV) for an activity is regularly calculated and compared with the PV and with actual cost (AC). This analysis, plotted graphically, reveals whether or not the project is going to plan. If it varies from the plan, it provides a time or cost figure for the amount of the variance. Remedial action can then be taken wherever necessary.
For more information about key issues involved in developing and managing project schedules, view: