I am applying for admission to several CS PhD programs (in the US), and I am just wondering how common it is for schools to request interviews with the candidates. I will be out of the country for much of January which seems like a prime time for interviews to take place, so I am wondering if I should start making alternate plans. Thank you!
I understand that interviews are fairly common in other fields and in other countries, but they are rare in computer science in the US. In my experience (student, postdoc, or faculty at five different American CS departments; multiple years on graduate admissions committees; dozens of recommendation letters for CS undergraduates applying to graduate school), very few (if any) American computer science departments include interviews as a standard part of the PhD application process.
There are rare exceptions, though, usually involving prospective advisors calling up applicants directly. The most common reason for a phone interview in my department is to assess their English fluency, especially when the applicant's test scores are borderline, or there seems to be a discrepancy between their test scores and the fluency of their statements. I'd be surprised if this happens more than 10 times a year, and we get 2000 grad applications each year.
When I applied to Berkeley's PhD program, I was already a PhD student at UC Irvine. My future advisor and the director of grad admissions called me to ask why I wanted to move when I seemed to be succeeding in my current program (good advisor, good research progress, and so on). I suspect they also wanted to understand the discrepancy betwen my grad school grades (good) and my undergrad grades (terrible).
In short, as long as there's nothing borderline or non-standard in your application, it's unlikely that you'd need to be available for an interview. And even if someone does want to interview you, they're much more likely to want to do it by phone or skype than in person.
From what I've seen, some form of interview is not uncommon (and a good sign, since it means you've passed most of the initial filters and are being considered seriously). In such cases as there is an interview, however, it can often be conducted over the phone or internet. Thus, your travel is unlikely to be a major issue as long as you will have good connectivity and be able to receive messages sent to the contact information you provided.