The phrase "large subset" refers to a specific group of things that is quite big but not necessarily including everything from the entire group. Full definition
However, less is known about potential adverse health outcomes among the much larger subset of individuals with antisocial behaviour limited to adolescence. (jech.bmj.com)
Any form of swaddling would benefit a very large subset of patients. (statnews.com)
Analysis of multiple cohorts of consumers around the world featuring large subsets of people on vegan and vegetarian diets — including the Adventist Health Study 2 in the US, the EPIC Oxford study in the UK and the Tzu Chi Health Study 1 and vegetarian... (foodnavigator-usa.com)