We look at estimates of size, effort, duration and cost; how people have gone about estimating their projects; the accuracy of the estimates and the relationships between estimates. Here are some of the findings:
- Size estimates are usually based on a data model; functional specification or analogy with a previous project
- Project effort estimates are only accurate for less than a quarter of projects
- Despite effort being poorly estimated 51% of projects were delivered on time
- When functional size-based techniques are used for a cost estimate, the estimate is within 20% of the actual cost 90% of the time.