The Big Y is a Y-chromosome direct paternal line test. It is designed to explore deep ancestral links on the common paternal tree. This test examines thousands of known branch markers as well as millions of places where there may be new branch markers.
The Big Y test is intended for users with an interest in advancing science. It may also be of interest to genealogy researchers of a specific lineage. However, it is not a test for matching a man to one or more men with the same surname in the way that FTDNA's other Y-STR tests do, such as Y-37, Y-67, and Y-111.
We cannot use Big Y results for grouping men into family groups in our Phillips DNA Project.