I interviewed for Analyst position with Oliver Wyman. Prior to interview I undertook online assessment test. My first interview was great. The interviewer was nice in speaking and calm and appreciated my inputs on case. Once I cleared first interview, I had second round. The second round was with an interviewer who was senior executive at the office. He called me a bit late and said that we will have to rush through the interview to which I agreed. After that we had typical interview questions and moved to case. I was well aware that I had to rush through the case given the time limit, so I made an assumption which was not acceptable and this created negative impact. So my advice would be to stick the rules of case solving, it would be fine to ask if you can make an assumption but be prepared to justify it .