Expert judgment in software effort estimation requires someone with previous experience in effort estimation who knows and understands the task under consideration to provide an approximation of effort. Expert judgment utilizes the knowledge of an expert and is a widely used strategy for software estimating. However, expert judgment can exhibit bias by the estimator and relies on the expert's previous experience on similar projects to generate a realistic estimate. Expert judgment comprises two approaches: effort-time and effort-size. Effort-time is an absolute value method, such as person-days or person-hours; effort-size is a relative measure such as story points or t-shirt sizing. Using a top-down approach that decomposes tasks into a granularity that is less than two days enhances expert judgment's accuracy and effectiveness. Large task estimation is prone to error and more challenging to estimate; thus, decomposition provides higher accuracy.
Expert judgment is ta common estimation technique used in effort estimation in software development. Although there is high availability of commercial estimation tools and approaches, expert estimation remains the most widely used estimation methodology. Expert-based effort estimates result from quantitative intuition as experts seldom base estimates on explicit analytical argumentation. Expert judgment is a non-algorithmic technique and may be prone to error as estimations can be inconsistent, lack repeatability, and be overly dependent on human memory. Estimation inaccuracies can stem from over-optimism and over-reliance on accuracy due to over-confidence in the estimator’s ability to deliver accurate estimations.