A study in the May 2012 issue of the journal Surgery found that the larger a residency program is, the more likely are its graduates to pass the written and oral board exams of the American Board of Surgery on their first attempt. Over the years 2006-2011, 85 percent of residents passed the written exam and 83 percent passed the oral exam on the first try.
The authors show linear regression lines with positive and statistically significant correlations between increasing size of a program and its residents’ first-time passage rates. They say, “This important finding may influence the application patterns and rank lists of medical students matching into general surgery residency programs.”
They mention only one limitation of the study, which is that they did not have first-hand knowledge of how the board passage data were produced. They apparently could think of no other potential confounding factors.
I can think of two right offhand.