You are managing a software development project using an agile approach. You divided the project into five iterations that are typically time-boxed to 30 days. You are estimating activity durations for the first iteration, and when taking a vote, three of your five team members hold up one finger. You spend some time understanding their concerns, make some adjustments in the iteration, and finally come to an agreement. Which of the following techniques could prove to be helpful in this context?