I applied to Columbia ed with an intended major of operations research. I see that many kids want to major in biology/biomedical engineering at Columbia. I assume that the number of people who are interested in operations research must be less. Approximately how many people are there applying to that program? Are my chances higher than a person applying to more popular engineering branches such as computer engineering?
I am sorry that I do not know the answer to your question. However, I do have a degree in OR. It is a very interesting subject and can lead to a very strong career.
There is another recent thread related to OR at Columbia.
There was a thread a couple of years ago regarding whether Columbia admits by major. If I am reading this correctly it appears that if you are applying to anything in engineering, which specific major within engineering does not matter:
http://talk.qa.collegeconfidential.com/columbia-university/2102981-does-columbia-admit-by-major.html
If you have already applied, then I would figure that you have already applied ED to a great program, and that Columbia is a reach for almost all students. You can try to relax, work on other applications, and hope for the best.