This might already have been mentioned, but this page describes how the rankings were done:
Also, for the first time, U.S. News is ranking Ph.D. programs in statistics. These rankings are based solely on the rating of academics at statistics and biostatistics departments.
I myself am looking into Masters programs in Statistics but now that I realize the US News rankings are only for PhD programs, I have to continue searching for some sort of guidance on which Masters programs are good.