Overview
The Duration Variance Percentage metric is used for measure project duration (or delivery time) performance with
respect to project duration estimates. This is frequently used to evaluate schedule management performance for both
individual projects as well as project portfolios.
Measurement Method
Cost Variance = (Planned Project Duration - Actual Project Duration) / Planned Project Duration - where
Planned Project Duration = Original estimated project duration for a specified completed project, defined as the
planned elapsed time period from the standard project start milestone (e.g., project kickoff date) to the standard
project completion milestone (e.g., application deployment date). Duration can be quantified in terms of a common unit
of time (e.g., days, weeks, months etc.).
Actual Project Duration = Actual project duration for a specified completed project, defined as the actual elapsed time
period from the standard project start milestone to the standard project completion milestone. Duration must be
quantified in the same units as Planned Project Duration, above.
The same formula can be used to evaluate multiple projects within a project portfolio for a defined evaluation period
through histograms or scatter distribution charts.
Measurement Analysis
Duration Variance Percentage indicates how accurately projects are able to estimate actual delivery time, or
alternatively, how well projects are able to deliver their defined project objectives within their original planned
duration. Rendered as a percentage, this metric facilitates trend charting and comparisons from period to period to
determine schedule management performance over time.
Duration Variance Percentage should fall between optimal values, frequently ranging from +/- 5% to +/- 30%. However,
the optimal range is dependent on the type of project(s) under evaluation. For example, highly predictable projects,
such as maintenance or small enhancement projects, require a narrower range of evaluation (say, +/- 5%), whereas highly
risky projects require a wider range of evaluation (say, +/- 30%). Additional ranges may be used to establish tiered
evaluation to characterize low, moderate, high variance conditions.
Upon establishing the evaluation ranges, if a project falls within the optimal range, the project is evaluated with
optimal delivery time performance.
Otherwise, the project is evaluated at a lower level of delivery time performance. Alternatively, a multi-period
histogram as below can classify portions of project portfolios by Duration Variance Percentage. This allows evaluation
of portfolio performance from period to period.
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