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 (Shekhar & Kumar, 2016). 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 (Khuat & Le, 2016). Expert judgment comprises two approaches: effort-time and effort-size (Arifin et al., 2017). Effort-time is an absolute value method, such as person-days or person-hours; effort-size is a relative measure such as story points (Arifin et al., 2017) or t-shirt sizing. McConnell (2006) states that using a top-down approach that decomposes tasks into a granularity that is less than about two days enhances the accuracy and effectiveness of expert judgment. Large task estimation is prone to error and more challenging to estimate; thus, decomposition provides higher accuracy.
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Expert judgement is a technique that involves using the experience and knowledge of subject matter experts to estimate tasks, project schedules, or costs. This approach is typically used when there isn't a lot of quantitative data available, or when the project is unique and there aren't previous similar projects to use as a reference.
The key steps in the expert judgement process typically include:
Identifying Experts: This could be individuals from within the project team, from elsewhere within the organization, or even external consultants or stakeholders. The key is that these individuals should have significant experience and knowledge in the area being estimated.
Estimation: Each expert provides their own estimate independently, based on their expertise and judgement. It's important that they do this independently to avoid any influence or bias from others.
Aggregation: Once each expert has provided their estimate, these are then aggregated to produce a single estimate. This could be done by simply taking the average or median of the estimates, or using more complex statistical techniques.
Discussion and Adjustment: The experts then discuss the estimates together, focusing on areas where there is significant disagreement. This discussion can often uncover important insights or issues that hadn't been considered initially. Based on this discussion, the experts may then adjust their estimates and the aggregation process is repeated.
Expert judgement is a powerful tool for project estimation, particularly for complex or unprecedented projects. However, it's important to remember that it is still based on individual judgement and can therefore be subjective and prone to biases. Therefore, it's often beneficial to use it in combination with other estimation techniques and to reassess estimates as more information becomes available during the project.