Meaning
Measurement of the degree to which the final cost of a project corresponds to its initial budget projection. High levels of estimate accuracy indicate that the planning team successfully identified all major risks and quantified the required resources. This metric is the primary indicator of the health of an organization’s project development process.
Performance Variance
Difference between the predicted financial outcome and the actual amount spent at the end of the job. Tracking estimate accuracy over multiple projects allows a company to identify systematic biases in its bidding or planning teams. If projects consistently finish over budget the organization may need to adjust its contingency factors or improve its data collection methods.
Confidence Interval
Range of possible outcomes where the final cost is expected to fall based on a specific probability. Reports on estimate accuracy often include a high and low range to show the sensitivity of the budget to external factors. A narrow range suggests that the project scope is well understood while a wide range warns of substantial technical or market unknowns.
Managers use these intervals to communicate the level of financial risk to the stakeholders before a final investment decision is reached. A project with a wide confidence interval may require more front end engineering to narrow the gap between the best and worst case scenarios.
Predictive Limit
Boundary of reliability for a budget based on the quality of the data available at the time of the forecast. Early in the lifecycle the estimate accuracy is low because many details about the site conditions and material costs are still missing. As engineering progresses the uncertainty decreases and the ability of the team to hit the target figure improves.
