How do you estimate on an Agile project?

Estimation can be a difficult beast to deal with; more so on an Agile project. How do you estimate when you don’t have a list of requirements that is complete or signed-off by the customer? Or a nailed-down schedule? What should your currency of estimation be? How do you estimate on a distributed team? Is it worth estimating at all? In this ebook we explore various perspectives on estimation beginning at the very root – What is the purpose of estimation?