The Trend Based solution method is the simplest and easiest way to generate a new estimate that reflects average schedule and effort performance for a project of a given size. It is the default solution method for new Estimation projects.
To create a new Trend Based solution, click the Create New Project from Template icon from the project list page, then select Estimation from the list of project types. Select a configuration source, then OK to go to the Assumptions tab of the Edit Estimate dialog.
If you are working with an existing project, you can just select Trend Based from the solution methods listed on the Assumptions tab.