Looking on the internet deeply has found these results:

I am in the university is the most popular phrase on the web.

I am at the university 11,170,000 results on the web	I am in the university 13,130,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
I send my most difficult samples to the university, but I am confident I am correct. I am chairing the Fundraising Committee of the University of Vienna's Summer School. I am Dean of the university's Natural Science Department, so... the museum is my responsibility. I am Professor Nasrin Mehani, director of the university program. No, I am professor of scientific atheism in the university. I am creating a research center of my own at the University of Miami. I am at the University of Michigan getting my PhD in French literature. I am currently on leave from the University of Athens.	I am at the University of Michigan getting my PhD in French literature. I am Professor Nasrin Mehani, director of the university program. I am currently on leave from the University of Athens. I send my most difficult samples to the university, but I am confident I am correct. No, I am professor of scientific atheism in the university. I am chairing the Fundraising Committee of the University of Vienna's Summer School. I am creating a research center of my own at the University of Miami. I am Dean of the university's Natural Science Department, so... the museum is my responsibility.

I am at the university

11,170,000 results on the web

I am in the university

13,130,000 results on the web

More popular!

I send my most difficult samples to the university, but I am confident I am correct.
I am chairing the Fundraising Committee of the University of Vienna's Summer School.
I am Dean of the university's Natural Science Department, so... the museum is my responsibility.
I am Professor Nasrin Mehani, director of the university program.
No, I am professor of scientific atheism in the university.
I am creating a research center of my own at the University of Miami.
I am at the University of Michigan getting my PhD in French literature.
I am currently on leave from the University of Athens.

I am at the University of Michigan getting my PhD in French literature.
I am Professor Nasrin Mehani, director of the university program.
I am currently on leave from the University of Athens.
I send my most difficult samples to the university, but I am confident I am correct.
No, I am professor of scientific atheism in the university.
I am chairing the Fundraising Committee of the University of Vienna's Summer School.
I am creating a research center of my own at the University of Miami.
I am Dean of the university's Natural Science Department, so... the museum is my responsibility.