What are my chances of getting into Yale, Penn or Duke?

What is your GPA (or equivalent), and your standardized test scores?

You might want to look at the Common Data Set for each school – generally Section C, and specifically Section C1, Section C7, and Sections C9-C11. Section C1 give the number of students who applied, were admitted, and then enrolled for a given academic year; Section C7 gives the academic and non-academic admission factors considered, and the weight attached to them, by the school; and Sections C9-C11 give date on GPAs and standardized test scores for first-year students who matriculated at each school for any given year. Review of this information from the CDS from each school may give you some insights into your chances for admission.