求助U.S.News 排名什么叫Tier 2？

AnttiZhang

TOP: 10 e.g. MIT Harvard
1st tier 10-30  e,g John Hopkings, umich
2nd tier 30-60 e,g UIUC, GIT
3nd tier 60-100 e,g Purdue, Indiana
Others NR e,g Northern Illinois University, parkland college