An example of a conceptual model diagram is the input-environment-output (IEO) model by Alexander Astin. This model is part of Astin's theory of involvement, which was published in 1984.
Astin's theory of involvement assumes students learn more by being involved in the social aspects of college life as well as academics. The IEO model shows how outcomes are linked to certain inputs and environments. Inputs include a student's background, demographics and previous life experiences. Environment refers to all of the experiences a student has while attending college. Related outcomes include the beliefs, attitudes, personal characteristics, and values that exist after a student graduates from college.