As part of their job, professors have to take care of getting funding, prepare classes, advise students, fulfill administrative tasks and attend to various meetings/conferences.
How much time do professors have to carry out research on their own (i.e. excluding the above-mentioned tasks)?
I am especially interested in the field of computer science > machine learning, in the US, in an averaged-size university.
I am mostly looking for studies that try to quantify how much time professors have to carry out research on their own.