The science of estimation produces somewhat different results than the informal comparison to past projects does. If you plug the same assumptions into Construx Estimate (that is, using the historical data listed to calibrate the estimate), you get an expected result of 80 staff months, which is in the middle of the range produced by the less-formal approach. Construx Estimate gives a Best Case estimate (20% confident) of 65 staff months, and a Worst Case (80% confident) estimate of 94 staff months.
When Construx Estimate is calibrated with industry-average data instead of historical data, it produces a nominal estimate of 84 staff months and a 20% to 80% range of 47 to 216 staff months, which is a much wider range. This again highlights the benefit of using historical data, whenever possible.
Tip #85 | Use software tools based on the science of estimation to most accurately compute effort estimates from your size estimates. |