It is impossible to anticipate every single potential interview question, so you should expect to be caught off guard at some point in the interview. The key is how you choose to respond when faced with this situation. Things to think about:
1) Remember that it is perfectly okay to take some time to think about an answer. You may say something such as, “that’s a great question. Let me take a few seconds and think about a good example.” As an interviewer, I would much rather wait for 20 seconds for a response, rather than hearing a terrible answer.
2) If the question is very technical in nature and you don’t have an answer, you should be honest. For example, in a finance interview the interviewer may ask you to explain the “beta” of a stock. If you have no idea what “beta” is you can say the following:“Unfortunately, I am not sure what “beta” means but I am looking forward to learning more about finance during my summer internship experience. I am also currently enrolled in a Corporate Finance class and I anticipate that we will cover this topic.”
3) Another approach to a question you don’t know the answer to is to say something about what you do know the answer to (must be related). Here’s an example to a question about your view of Brazil’s economy. “Although I have not had the chance to follow recent news about the Brazilian Economy, I do follow the other emerging markets, especially India and China. India recently… ” (continue with analysis).
FYI: Beta describes excess stock returns over excess market returns. Or, more simply, how the return of a specific stock compares with the return of the market as a whole.