What makes certain hospitals number one in something? how do they determine that one is better than another in a certain field.

Murky subject: They're ranked using various methods that weigh many factors (reputation, mortality, preventable complications, volume, staffing ratio, etc) differently. Thus, the same set of hospitals could be put through different rating systems (with different factors and weighting of factors) and come out with different rankings. http://www.usnews.com/pubfiles/BH_2014_Methodology_Report_Final_Jul14.pdf