AACE defines the maturity of project definition as the primary factor determining an estimate’s class. This presentation clarifies misconceptions about estimate accuracy and its relationship to project definition. It explores client expectations, intended estimate uses, and factors that genuinely influence accuracy—while identifying practices that only appear to improve accuracy but actually undermine it.

By distinguishing poor practices from best practices, estimators can avoid distractions and focus on methods that deliver reliable, defensible results. Likewise, understanding common missteps enables estimate recipients to recognize and correct deviations early, reducing cost and risk.

Topics include misuse of historical data, reliance on conjectural deliverables rather than sound engineering, and the false assumption that multiple small inaccuracies are harmless—when collectively they can distort results. The authors draw on real-world experience to illustrate how disciplined estimating practices lead to more accurate and effective project outcomes.