Since i'm a contractor i get interviewed a lot, i sometimes come up against these brainteasers which i usually dont mind. Sometimes they're good questions like how would i solve problem X using X language, because thats relevant, i think its a good question.
However, i hate when i get questions like "how many golf balls can you get in a double decker bus" and "whats your most embarrassing moment", both of these were questions i was actually asked in an interview. My answer to the first was "I dont know and i'm not going to try and work it out because 1) i dont have enough information and 2) its not relevant to this position. I'd happily answer hypothetical questions about situations that could plausibly come up during this position, but working out number of golf balls in a bus doesnt show you how i would solve the problem of the database running slow or validation checks not working correctly." For the second one i simply answered "I have never been embarrassed in a professional setting as i mainly just do my job and i'm not embarrassed to say 'I dont know' or to ask for help. The only times i've been embarrassed were in my personal life and those are stories not appropriate for an interview."
Needless to say, these were questions asked by the CEO of a startup i thought was absolutely amazing, i had sat through a tech interview with the CTO before the CEO came in and felt i did well with the tech questions. Once the CEO came in and asked me these questions, i wondered how an awesome startup was achieving this success behind the leadership of total and utter moron. I decided not to work there as i lost all respect for the CEO.
I used to take this a step further. The split second one of the silly questions popped up, I'd stand up and very politely end the interview. Reactions were priceless. Interestingly, I'd often get invited back, or on a couple of occasion offered the job after a follow up phone call, where I give the sort of responses you have given.
The problem I have is that these types of question suggest to me that the company doesn't really know what it wants to hire, and there for is not one I would want to work for.
The problem most people have is that they really need the job and feel compelled to play along, which I can only assume these interviewers take as positive feed back.
There could be a chance that they are simply testing you to see how you respond to silly questions and how much of a stuck up asshole someone can be (not that you are one).
I'd imagine it's a good way to spot well adjusted human beings.
This, of course, assumes (positive) things about the company and the interview process, which may not be true for 95% of the sample as far as I know.
> "how many golf balls can you get in a double decker bus"...
> 1) i don't have enough information and 2) its not relevant to this position.
Whilst I agree somewhat with the sentiment, I don't think that's at all an unreasonable question.
1. You do very clearly have enough information to make a decent informed guess.
2. It is a relevant question.
It's relevant because it assesses your general sense of numeracy. Whilst that won't show how quickly you'd be able to deal with a database issue, it does give an indication of how you might go about making broad judgement calls in the absence of any hard-and-fast numbers. For example: Is it worth looking into this database issue, or is it likely to be insignificant compared to the network overhead?
But if that's the information you're after, why ask for golf balls and busses? These are real world quantities with decidedly different qualities than whatever appears in standard computing scenarios. Describing how you'd go about troubleshooting a three layer architecture with inordinate network load on the database might be a better question then?
I actually think that's a decent question - in many cases you have to estimate something based on incomplete information in a domain that you aren't an expert in and maybe all you are after is an answer to the nearest order of magnitude.
In my experience some people simply won't answer those questions - not because they can't but because they aren't happy working that way. Of course, in some situations you absolutely do need people who will always work things through from first principles and attempt to give as precise an estimate as they can, but sometimes you don't.
really what sort of bus? Routemaster ,Bendy Bus, one of those new Boris busses, a US school Bus. Also how does one easily estimate the free space inside a bus. How many pasendgers are there with or with out a driver or conducter can I remove the seats and other furnature inside.
Of course one can trivialy estimate the number if one assumes that bus is a cuboid and that a golfball is an incompressble sphere - I would would probly have to look up the theorems on Google as its a long time since I used this sort of thing in anger - though bak in the day I did correct a bridge design for the 4th largest consulting engineers when the Engineer had use 2d rather than 3d :-)
It could also be a culture question. I worked on a trading floor and we'd make "markets" on when lunch would arrive, the cost of an airline ticket, the number of times I would injure myself in a week, etc. While there are more precise ways to ascertain a potential hire's arithmetic and estimation skills, this is more fun (especially since the interviewee's answer would usually kick off a round of bets being placed by the team on what they thought the answer was - this had the added benefit of giving us a relevant distribution to test the candidate's answer against).
It also drew out people who may not be a fit for our desk's culture of camaraderie where answers to banter along the lines of "that's personal" or "that's not relevant to my job description" would be awkward at best.
Additionally, I have heard from consulting buddies (the heathens!) that it's can good way to see how well a candidate can bullshit on little to no relevant data.
In any case, I don't think it's empirically valid to conclude someone a moron for asking brain teasers in interviews. I never asked them whereas many people much smarter than me did.
The purpose of this type of interview question is, per my argument, to get an idea of cultural fit and estimation skills. Like any measure it picks up some signal and a lot of noise, e.g. bullshitting skills. The trick is to combine measures such that the noise largely cancels out while preserving the signal.
If this were the only type of interview question used the points you brought up would be a legitimate concern. Given that it was, in my case, married in a much greater proportion with concrete questions I maintain that it generated unique, useful information.
Traders generally have, prior to entering a trade, the opportunity to think through everything thoroughly and ask for help on the bumps. There are also times when the cost of the time for analysis is so great that a gut, if rough, call is needed, e.g. holding hard drive manufacturer equity as news of Bangkok flooding breaks. Being able to ball-park figures, after issuing a disclaimer about the uncertainty of one's estimates, is also a generally useful analytic skill.
It should also be noted that part of recognising the priority of things to be analysed is the degree by which they deviate from expectations - generating many of those expectations is a form of intuitive estimation.
But, as I said, it's mostly to estimate whether this is a person we'd like to spend 10-16 hours a day near. Constant righteous indignation would probably get annoying as fast as serial bullshitting.
I think "how many golf balls can you get in a double decker bus" is a fair question for assessing whether someone can apply basic maths to a to a real life (i.e. not perfectly defined) problem. If that's a skill the job needs it's a perfectly reasonable question.
I also think it's a fair question, but more about logical reasoning and estimating than basic maths. As an engineer, you could be asked to estimate the number of load balancers needed for X traffic with Y latency - similar problem.
In my experience of those kinds of problems the catch is finding realistic values for X and Y - often nobody is going to hand them to you on a plate and you must work out a way of estimating them - that is the real skill.
But Fermi problems are quite relevant in computing work. Here is a question I was asked recently:
"How many users do you think will ever concurrently use a certain subset of our website?"
Actually, the question was phrased as "how would you architect Feature X?" This naturally led to "do we need a distributed approach?" And of course, the answer to that depends on the answers to the Fermi question and "how many users can a single box handle".
I've never been asked a to solve a Fermi problem in an interview, but I would most likely require that the interviewer give me the data I need. In the golf ball example, I would ask for diameter of the golf ball, dimensions of a bus, etc. Otherwise they're just asking me to prove that I have seen a golf ball up close, that I've been riding on double-decker buses and that I'm decent at measuring physical objects with my eyes.
Or you could guesstimate a diameter of a golf ball and then tell them how much the answer could change as a function of your error, rather than demanding perfect information in an imperfect world.
The goal is not to get a precise answer, the goal is to see how you think.
Sorry, I didn't mean to imply I wanted precise information. Their guesstimate is going to be better than mine, which is why I would ask them for that info. I'm just not comfortable with pulling data out of my lower dorsal region. And I guess that's the part of how I think.
Another reason I like Fermi problems, is that the kind of people who I want work with (read: curious-minded tend-to-be-geeky programmers) tend to love them, and solve them for fun. I can't count the number of times we sat over lunch, arguing weird questions like how many planes it would take to move a certain river, or how many people it would take to eat a rhinocerous.
If someone is put off by these kinds of questions, I would question whether they fit with the kind of culture I think a group of smart people have.
> "how many golf balls can you get in a double decker bus"
> My answer to the first was "I dont know and i'm not going to try and work it out because 1) i dont have enough information and 2) its not relevant to this position.
The genesis of these kind of questions is http://en.wikipedia.org/wiki/Fermi_problem (checkout the classic "how many piano tuners"). Fermi approximation's purpose it to estimate without concrete data. In the end, if the numbers aren't right, you just need to replace the numbers, provided your method was correct.
I am not contending its relevance(largely irrelevant). I am just pointing out the origin.
The CEO doesn't know the answer to how many golf balls so he wasn't looking for the end result, he was looking for where you start when problem solving. Many people have no idea how to start solving a problem they haven't seen solved before. The question is valid and you sir are grumpy. But I do give you kudos of standing up for your opinions, that is a trait I'd like in someone I'm hiring.
> working out number of golf balls in a bus doesnt show you how i would solve the problem of the database running slow
What about estimating how many I/O operations in a second the DB supports? You'd be surprised how many candidates out there lack basic arithmetic abilities.
I have never heard of anyone being asked "what's your most embarrassing moment?" What a bizarre question. Clearly, my most embarrassing moment, whatever it may be, is far too embarrassing for me to go around telling random strangers about.
The only utility I can see in that question is to assume that it's a question you're expected to dodge, and that the deftness with which you deflect the crazy question is a measure of your interpersonal skills. To launch into a story about this one time at band camp is presumably the worst possible answer.
Still, I don't think it's good even for that question.
The correct answer is a funny anecdote that is only mildly embarrassing at best. Bonus points if you can make yourself look resourceful and/or humble at the same time.
However, i hate when i get questions like "how many golf balls can you get in a double decker bus" and "whats your most embarrassing moment", both of these were questions i was actually asked in an interview. My answer to the first was "I dont know and i'm not going to try and work it out because 1) i dont have enough information and 2) its not relevant to this position. I'd happily answer hypothetical questions about situations that could plausibly come up during this position, but working out number of golf balls in a bus doesnt show you how i would solve the problem of the database running slow or validation checks not working correctly." For the second one i simply answered "I have never been embarrassed in a professional setting as i mainly just do my job and i'm not embarrassed to say 'I dont know' or to ask for help. The only times i've been embarrassed were in my personal life and those are stories not appropriate for an interview."
Needless to say, these were questions asked by the CEO of a startup i thought was absolutely amazing, i had sat through a tech interview with the CTO before the CEO came in and felt i did well with the tech questions. Once the CEO came in and asked me these questions, i wondered how an awesome startup was achieving this success behind the leadership of total and utter moron. I decided not to work there as i lost all respect for the CEO.