Heh...just had an interview with Analytic Partners in midtown the other day. Accidentally blew a question that you had a 4x4x4 cube and you removed one layer from each side. I said 4 brainlessly in the beginning, talked through it, and realized it was eight (palmfaced myself then and there) because I knew what I was doing and thinking in terms of 2s and 2s, but my mind just slammed on four by accident. Still got the right answer, but not before blurting out a rushed answer...honestly, I like the kinds of questions in the quantitative interview questions thread better that I don't feel like I'm supposed to nail it in 5 seconds, because the slightest tinge of nervousness can screw it up then and there.
Here's another question I got:
A company has a rental car for every 1000 people. How much mileage on one car can they expect in a year?
My answer: assuming that people take the car out for a work day's amount of time, and that the car is always in use, the car gets driven three round trips a day, and say, for ten miles one way to a destination. Since there's approximately 50 weeks in a year and the cars are driven five days a week (work days), each car will have approximately 60 x 5 x 50 = 15000 miles on it in a year.
I don't think you did THAT badly. You corrected yourself before the interviewer told you you were wrong; in a researcher's, quant's, or financial programmer's book, that's still pretty acceptable. For a trader, it might not be. You don't have to be perfect, but you do have to be comfortable with numbers.
Just smile. One thing that I do in interviews is, "Just a sec, I need a minute to think about this." It takes some of the pressure off; you don't have to be lightning fast with the stuff you're not expected to know off the bat. I work on a fixed income analytics system and I can be expected to know the definitions (both mathematical summary and casual explanation) of the biggest risk measures without flinching, but if they ask me to price something or throw me a question from left field, I have every right to take my time and think- especially if I smile and comment that it's a really good (or tough) question.
One of the things that always happens in a technology- and often finance or engineering interview- are questions about "Have you seen this?" Two years ago, when I was interviewing for my first job, I would invariably say yes if I had remotely seen it. The problem is that those initial questions usually have something really tough lurking behind them. Now that I'm older and wiser, unless I know the subject like the back of my hand, my response is to smile and say, "'Seen' is a strong word if you're about to ask me a really tough question, but I'd like to take a crack at whatever you've got for me." If the interviewer's in a good mood, he'll laugh and give me the question. There won't be anywhere near as much pressure on me, and 75% of the time, I'll get the right answer, anyway.
Your resume is a marketing document, but the strategy in the interview is to downplay, downplay, downplay unless you really know something well. Manage the interviewer's expectations, and he'll come out of the interview thinking, "Wow. That kid didn't claim to know much about stochastic calculus, but he derived the black-scholes formula in five minutes." rather than, "This kid claimed to know everything, but he couldn't answer half my questions." This strategy tends to have a positive impact on
most interviewers.
That said, the strategy doesn't work quite as well with interviews with traders (particularly the guys who focus on executing short-term trades- like brokers, market-makers, or scalpers). They cut through BS, ask pointed questions that they have already irrevocably deemed you incompetent of if you cannot answer before you even open your mouth, and want an answer fast. They are the epitome of the J-type personality on the Meyers-Briggs scale and show no mercy. If you can survive one of these kinds of interviews- and you'll know it when you're in one- without saying "I don't know" or leaving an awkward silence, you've probably done just fine.
Those interview books you bought for trading don't apply for analytics, banking, research, quant work, or technology (and the rules for the latter five are actually pretty similar). For the non-traders, just underpromise (at least in the interview), overdeliver, and if you have the opportunity, provide some tactful comic relief with a smile.
