The second ratio is the schedule performance index (SPI), which is defined by the ration EV/PV. This ratio is a measure of how close the project is to performing work as it was planned to occur. Values of SPI greater than one indicate an ahead-of-schedule situation. Values less than one are indicative of a project that is behind schedule. These values can also be tracked over time to detect any trends that might suggest best practices or potential problems for the project being tracked. Whichever is the case, a follow-up action plan should be formulated. SPI history is a valuable input to the project review.
Figure 4.2 gives an example of a situation where both performance indexes are positive. This project has accomplished more than was planned to be accomplished at this point in time and did it with less expenditures than were planned. Ahead of schedule and under budget—this is the best of all possible worlds. When a project displays this type of performance, it is important to our improvement initiatives that we investigate the reason for the exemplary performance. The project review may bring those practices to light but a more investigative process might be needed as well. There may be some best practices hidden beneath the covers of this project. We would want to find out what they are and share them with other projects to the extent possible.
Another metric for tracking the project schedule over time is the Milestone Trend Chart (MTC). The MTC was introduced in my book Effective Project Management [ 1], which can be referred to for a more complete discussion. Each trend chart tracks a single future milestone event in the project. At each reporting period (weekly or monthly) an updated estimate of the date on which the future milestone event will occur is made. The estimate should be generated by the software package you are using to track the project. Once the work completed since the last report date and the revised estimates to completion are input to the project file, new estimated completion dates of all future tasks are calculated by the software package. The trend in these forecasted dates over time is predictive of the general health and performance of the project. Several milestone events may be tracked for a single project. One milestone event that will be particularly interesting is the completion date of the project. Other milestone events of interest might be the approval of significant phases in the project, such as design or subsystem testing. In the following sections we take a look at several examples and ask the question: "What can we learn about PP based on the project's milestone trends?"
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What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.