I applied through an employee referral and heard back within a day. I had an initial phone interview with HR. HR missed the initial interview time, but then emailed me to apologize and explain the situation. We were able to reschedule for later the day. Very basic interview, 30 minutes long. She asked a lot about my resume, research experience, and presentation experience. Received an email the next day saying I had moved on to the second round. This was to be a 1-hour phone interview and a writing exam. It took me about a month to schedule it because the HR person was out of the office for a week. I kept following up, but then it was the winter holiday, so I received no response, not even a computer-generated email saying that they were out of the office. It was a bit annoying. Finally heard back i the new year with more details about the second interview and writing exam. Second interview consisted of 30-minute behavioral and 30-minute case questions. Behavioral questions were straightforward and asked more about my experiences and how I respond to different situations. Case interview was relatively easy and consisted of no math. The writing exam was similar to the case interview. I received an email the next day saying I had moved to the third round, in the DC office. Interviews were to be similar as the second stage one. I had a total of two. The first one was easy and straightforward. The case also had no math. For the second interview, my interviewer was 15 minutes late. He showed up in a baseball cap and jeans and told me he would have to cut the interview 15 minutes early. He was also pretty cocky about it. I thought it was pretty rude. He asked me about an experience on my resume, then focused on the case interview. This one had math. All in all, a pretty strange interview experience, especially the in-person one.