Which estimation method is commonly used in agile methodologies?

In agile methodologies, the use of story points is a prevalent estimation method because it allows teams to assess the complexity, effort, and size of work items in a relative manner. Story points provide a way to estimate the effort required to complete a given task or user story without specifying the exact duration or hours. This method emphasizes the uncertainty and variability of estimating actual time and focuses instead on how much work the team believes can be accomplished in a sprint based on previous experiences.

Using story points encourages collaboration among team members as they discuss and agree upon the complexity of various tasks. This collaborative effort often leads to more accurate estimates because it captures diverse perspectives and insights. Furthermore, story points can enhance the team's ability to measure progress and velocity over time, allowing them to adapt their planning as they become more familiar with their capacity and workflow.

Other methods listed may not align with agile principles; for example, estimation by consensus can be a part of the agile process, but it is not specific to it in the same way that story points are. Waterfall estimation and Critical Path Method are more suited to traditional project management approaches, which involve detailed upfront planning and a linear process, contrasting with the iterative and adaptive nature of agile methodologies.