A study at the University of Washington Information School showed that college students “frequently used Wikipedia for background information, but less often than they used other common resources, such as course readings and Google. Architecture, engineering, and science majors were more likely to use Wikipedia for course-related research than respondents in other majors.” (from American Libraries)
Alison J. Head and Michael B. Eisenberg (2010). How today's college students use Wikipedia for college-related research. First Monday, 15(3).