6 ms·

..and I will no longer be interested in the job if you think answering a question like that is a worthwhile use of my time, or yours. It's trivially easy to fi

by ebbv 14y ago

..and I will no longer be interested in the job if you think answering a question like that is a worthwhile use of my time, or yours. It's trivially easy to figure out how to calculate a rough number. I'd go so far as to say blatantly obvious. It's also a waste of time to actually do it. When it comes to the real world, an estimate that rough, based on no actual data (since the actual dimensions of a golf ball or the hypothetical, poorly defined bus are not available), is not something I'm ever comfortable acting on. In reality, you can always come up with better data than that.

DanBC 14y ago
No-one is interested in the number you come up with. They're interested whether or not you have a process you use to come up with that number. Ask some people how many golfballs fit in a bus. They'll be stumped. They'll have no idea how to proceed. They'll just stop, and look at you, and flounder. Ask other people and they'll have a problem solving process. They'll define the problem; they'll gather information; they'll make assumptions (and note the dangers of assumptions) and then they'll start to work out a rough solution. The number that plops out the end is not relevant. Unless your process comes out with a number that is clearly nonsense ("5" or "27 billion") and you ignore that.
- undantag 14y ago
  This. The most important takeaway from a face-to-face interview for me has always been to gauge a candidates general problem solving ability. When developing, you'll constantly be solving problems that are new to you, in areas you may not be familiar with.
  - EwanG 14y ago
    Because we presume that an interviewee is desperate enough that they won't give the "honest" answer - well, I'll google that and see if I can't find someone else who has already found the answer. Seriously, between Google and Wolfram Alpha, do you think that any of these inane questions can't be answered within a reasonable level of proximity? Don't believe me? I just googled "golf balls in a school bus" and had a page full of answers in seconds including how they solved it as well as the number. https://www.google.com/search?source=ig&hl=en&rlz=&q=golf+balls+in+a+school+bus https://www.google.com/search?source=ig&hl=en&rlz=&#... Better, why not ask me to pseudo-code a problem you've faced recently? Wouldn't that tell you a LOT more about whether my skills and your needs align?
    - yummyfajitas 14y ago
      Go use Google and Wolfram Alpha to find the answers to "how many fashion items are for sale on the internet?" If you can do that, I'm truly impressed by your google-fu. Also, as I said, the fashion items question is a problem I faced at my last job.
      - EwanG 14y ago
        I highlighted your question, right-clicked and chose to Google it, and it was answer number 3 on the returned results. I suspect Alpha would give more useful detail, but then I really think that wasn't what you were looking for. Slightly more seriously, going to Google first for ANY such problem would highlight both what is already known about the issue, and profitable answers to look for further information.
      - v0cab 14y ago
        Then why wouldn't you ask a real-world question like that, rather than a stupid one about filling a bus with golf balls?
    - DanBC 14y ago
      > Seriously, between Google and Wolfram Alpha, do you think that any of these inane questions can't be answered within a reasonable level of proximity? Using Google? 3 in 600 searches used the + operator, and of those 2 were wrong. Saying "I would understand the problem, I would work out a suitable search query, I would use available resources, I would evaluate the responses I got; here's the result when I used a typical question like this".
  - malandrew 14y ago
    The most important general problem solving skill is the ability to eliminate problems entirely so that you don't need to come up with a solution at all. I think it's prudent to know the etymology of the word problem, whose origin is in "proballein", which literally means "thing thrown forward", much like a hot potato. And like a hot potato, the easiest solution is to throw it forward until it cools down. i.e. it comes to rest with someone who no longer sees it as a problem. Handled elegantly and diplomatically, the "it's not my problem" approach to eliminating problems is a perfectly acceptable strategy, especially when you poorly understand the problem and the benefits of finding a solution. Eventually, if it is a problem worth solving, it will come to rest with the person who sees an opportunity in solving it and is equipped to do so. In fact, this is essentially the very basis of all rational economic activity.
- deleted 14y ago
  [deleted]
- planetguy 14y ago
  I agree with all your points, but also think one must be circumspect when applying this sort of question. You're right, some people, when faced with a question like this, will flounder. Maybe sixty percent of the population. The rest will all solve it in a similar sort of way. It's thus a bit of an "are you a complete idiot?" test, so by applying it you express an uncertainty over whether the person you're interviewing is a complete idiot. This is fine if you're interviewing fresh-faced undergraduates or something, not so good if you're interviewing someone with a long track record of success for a senior role. I don't interview people all that often, and the circumstances are such that by the time someone gets in front of me I can take it for granted that they're not a complete idiot. Thus, I feel no need to apply this kind of test.
- v0cab 14y ago
  Can I just say "I assume it's about 2000." and be done with it? I mean, that's a good enough estimate when we're not actually going to be putting golf balls on buses and are just chatting about it.
  - DanBC 14y ago
    The purpose[1] of an interview (for the interviewee) is to get the job. The purpose of the question is[2] to gauge the interviewee's ability to solve problems. With those constraints your approach would appear to be sub-optimal. Sometimes in life we have[3] to jump through hoops to get what we want. [1] Primary purpose; there are other things, such as deciding whether the company is a terrible place or full of idiots or etc. [2] Should be; I accept that maybe many people have heard about these questions and think they're the right thing to ask but have no idea of the purpose. [3] Or we decide that hoop jumping is not for us and we reject all hoop jumping and politely decline the job.
    - v0cab 14y ago
      The hoops are invisible in this case. It's a matter of putting on a show for the interviewer. But we don't know what kind of show. A show where we make assumptions about things? or ask questions? A show where we try to get as 'real-world' an answer as possible? or one where we assume things to make our lives easier? Why not just assume it's a toy bus and nothing can fit in it? Is that a clever and funny time-saving technique, or am I mocking the interviewer? But yeah, the candidate has to do what he has to do if he needs a job. I think that's what you're saying anyway.
- v0cab 14y ago
  > Ask some people how many golfballs fit in a bus. They'll be stumped. They'll have no idea how to proceed. They'll just stop, and look at you, and flounder. Because, as ebbv said, there is absolutely no way they can get a decent level of accuracy that would be useful for any kind of purpose. Any estimate in such a situation would be thrown away as soon as Google and other resources are available. Therefore they effectively cannot answer the question, and the question is useless.
- v0cab 14y ago
  > they'll make assumptions (and note the dangers of assumptions) So is it OK to make assumptions or not?
- michaelcampbell 14y ago
  > No-one is interested in the number you come up with. They're interested whether or not you have a process you use to come up with that number. Then ask, "How would you figure out how many golf balls fit in a bus?" This circuitous way around finding out what you want is anathema to most techie types anyway. My problem with these brainteaser type questions is the interviewer (in my experience) NEVER has had the experience or know-how to interpret the answer; all they have been able to do is get a level of "ah, interesting" type "gut feel" from it. If I'm interviewing with someone who's got the background to be able to analyze what I'm actually thinking, fine, but to date, I've not seen it.
Limes102 14y ago
I agree.. I would probably have left.. The questions either have subjective answers or are totally trivial.
- mistercow 14y ago
  How do you mean "subjective"? There is an objective answer to the question "how many golf balls can fit in a double decker bus" and while I suppose you could call it "trivial", being able to make that kind of estimate efficiently really is an important skill for programmers (and scientists, and engineers) to have. That said, this is another FizzBuzz sort of test, and should not be made unnecessarily complicated. This is what you're trying to filter out: http://www.youtube.com/watch?v=Qhm7-LEBznk http://www.youtube.com/watch?v=Qhm7-LEBznk
  - v0cab 14y ago
    There's so many different kinds of buses, and it clear what kind of level of accuracy is required. I can just say 'two thousand' and that's a good enough answer. The problem is, that isn't good, as the interviewer wants to 'see how I think'. But he hasn't really given me a problem to think about, so I have to just put on a show for him. He hasn't seen how I think at all; he's just seen me putting on a show based on what I think he wants to hear.
    - mistercow 14y ago
      >There's so many different kinds of buses There is a lot of variance in bus sizes, but not enough to put you off by more than an order of magnitude. > and it clear what kind of level of accuracy is required. Knowing what kind of accuracy is required is sort of part of the test. The parameters are vaguely specified, so you should know that you're looking at orders of magnitude. >I can just say 'two thousand' and that's a good enough answer. That would fit in a large duffle bag. If you told me that you thought you could only fit 2000 golf balls in a double decker bus, I would assume that you either put zero thought into answering the question, or that you did not have a good grasp of how to estimate things. > The problem is, that isn't good, as the interviewer wants to 'see how I think'. The interviewer wants to know that you can give sane estimates based on rough calculations. As the article explains, there are many, many situations where a programmer needs to be able to do this kind of thing. It's not about "seeing how you think". It's about seeing that you can think – at all – about estimation problems. > But he hasn't really given me a problem to think about, so I have to just put on a show for him. He hasn't seen how I think at all; he's just seen me putting on a show based on what I think he wants to hear. And if that show is "2000 balls", he has learned that he should not hire you.
rodly 14y ago
Why is it a waste of time if it gets you the job? The answer is "trivially easy" so it shouldn't take you long to waste your time on. I'd wager that you spent at least twice as much time writing up your response to this article than it would take to answer such an interview question. What's the true waste of time here?
ColinWright 14y ago
Like FizzBuzz, you over-estimate people's ability to do this. I know many programmers who are able to knock out a Rails App without breaking a sweat, but ask them to think about throughput, or simultaneous connections, or machine load, or disk access, or anything else requiring ballpark estimates and general arithmetic and they're lost. Sure, I know what I'm hiring you for today, but in a small company what you're doing today won't be what you're doing next month, unless you're so limited as to be unable to think outside your own existing speciality. Ability to adapt is critical. By the time I've got you to interview I already know you can program, and most likely you've already shown an interest in my company. If you're unable to have a hack at something just because you think it's unrealistic, or poorly defined, or just uninteresting, that tells me something about you. And to be fair, and in the interests of full disclosure, before I ask these questions I ask the candidate's opinion of them. In some cases that's already enough.
mistercow 14y ago
>It's trivially easy to figure out how to calculate a rough number. I'd go so far as to say blatantly obvious. It's also a waste of time to actually do it. Given any X, only a small minority of the people who believe they have the skills needed to do X competently are right. Dunning–Kruger as usual. It should be trivially easy to figure out roughly how many golf balls fit in a double-decker bus. In fact, it shouldn't take more than a few minutes of figuring, so the time wasted ought to be minimal. If it does take longer than a few minutes, then the interviewer has learned something important about you, so it's not a waste of time then either.
deleted 14y ago
[deleted]

by ebbv 14y ago

DanBC 14y ago

No-one is interested in the number you come up with. They're interested whether or not you have a process you use to come up with that number. Ask some people how many golfballs fit in a bus. They'll be stumped. They'll have no idea how to proceed. They'll just stop, and look at you, and flounder. Ask other people and they'll have a problem solving process. They'll define the problem; they'll gather information; they'll make assumptions (and note the dangers of assumptions) and then they'll start to work out a rough solution. The number that plops out the end is not relevant. Unless your process comes out with a number that is clearly nonsense ("5" or "27 billion") and you ignore that.

undantag 14y ago
This. The most important takeaway from a face-to-face interview for me has always been to gauge a candidates general problem solving ability. When developing, you'll constantly be solving problems that are new to you, in areas you may not be familiar with.
- EwanG 14y ago
  Because we presume that an interviewee is desperate enough that they won't give the "honest" answer - well, I'll google that and see if I can't find someone else who has already found the answer. Seriously, between Google and Wolfram Alpha, do you think that any of these inane questions can't be answered within a reasonable level of proximity? Don't believe me? I just googled "golf balls in a school bus" and had a page full of answers in seconds including how they solved it as well as the number. https://www.google.com/search?source=ig&hl=en&rlz=&q=golf+balls+in+a+school+bus https://www.google.com/search?source=ig&hl=en&rlz=&#... Better, why not ask me to pseudo-code a problem you've faced recently? Wouldn't that tell you a LOT more about whether my skills and your needs align?
  - yummyfajitas 14y ago
    Go use Google and Wolfram Alpha to find the answers to "how many fashion items are for sale on the internet?" If you can do that, I'm truly impressed by your google-fu. Also, as I said, the fashion items question is a problem I faced at my last job.
    - EwanG 14y ago
      I highlighted your question, right-clicked and chose to Google it, and it was answer number 3 on the returned results. I suspect Alpha would give more useful detail, but then I really think that wasn't what you were looking for. Slightly more seriously, going to Google first for ANY such problem would highlight both what is already known about the issue, and profitable answers to look for further information.
    - v0cab 14y ago
      Then why wouldn't you ask a real-world question like that, rather than a stupid one about filling a bus with golf balls?
  - DanBC 14y ago
    > Seriously, between Google and Wolfram Alpha, do you think that any of these inane questions can't be answered within a reasonable level of proximity? Using Google? 3 in 600 searches used the + operator, and of those 2 were wrong. Saying "I would understand the problem, I would work out a suitable search query, I would use available resources, I would evaluate the responses I got; here's the result when I used a typical question like this".
- malandrew 14y ago
  The most important general problem solving skill is the ability to eliminate problems entirely so that you don't need to come up with a solution at all. I think it's prudent to know the etymology of the word problem, whose origin is in "proballein", which literally means "thing thrown forward", much like a hot potato. And like a hot potato, the easiest solution is to throw it forward until it cools down. i.e. it comes to rest with someone who no longer sees it as a problem. Handled elegantly and diplomatically, the "it's not my problem" approach to eliminating problems is a perfectly acceptable strategy, especially when you poorly understand the problem and the benefits of finding a solution. Eventually, if it is a problem worth solving, it will come to rest with the person who sees an opportunity in solving it and is equipped to do so. In fact, this is essentially the very basis of all rational economic activity.
deleted 14y ago
[deleted]
planetguy 14y ago
I agree with all your points, but also think one must be circumspect when applying this sort of question. You're right, some people, when faced with a question like this, will flounder. Maybe sixty percent of the population. The rest will all solve it in a similar sort of way. It's thus a bit of an "are you a complete idiot?" test, so by applying it you express an uncertainty over whether the person you're interviewing is a complete idiot. This is fine if you're interviewing fresh-faced undergraduates or something, not so good if you're interviewing someone with a long track record of success for a senior role. I don't interview people all that often, and the circumstances are such that by the time someone gets in front of me I can take it for granted that they're not a complete idiot. Thus, I feel no need to apply this kind of test.
v0cab 14y ago
Can I just say "I assume it's about 2000." and be done with it? I mean, that's a good enough estimate when we're not actually going to be putting golf balls on buses and are just chatting about it.
- DanBC 14y ago
  The purpose[1] of an interview (for the interviewee) is to get the job. The purpose of the question is[2] to gauge the interviewee's ability to solve problems. With those constraints your approach would appear to be sub-optimal. Sometimes in life we have[3] to jump through hoops to get what we want. [1] Primary purpose; there are other things, such as deciding whether the company is a terrible place or full of idiots or etc. [2] Should be; I accept that maybe many people have heard about these questions and think they're the right thing to ask but have no idea of the purpose. [3] Or we decide that hoop jumping is not for us and we reject all hoop jumping and politely decline the job.
  - v0cab 14y ago
    The hoops are invisible in this case. It's a matter of putting on a show for the interviewer. But we don't know what kind of show. A show where we make assumptions about things? or ask questions? A show where we try to get as 'real-world' an answer as possible? or one where we assume things to make our lives easier? Why not just assume it's a toy bus and nothing can fit in it? Is that a clever and funny time-saving technique, or am I mocking the interviewer? But yeah, the candidate has to do what he has to do if he needs a job. I think that's what you're saying anyway.
v0cab 14y ago
> Ask some people how many golfballs fit in a bus. They'll be stumped. They'll have no idea how to proceed. They'll just stop, and look at you, and flounder. Because, as ebbv said, there is absolutely no way they can get a decent level of accuracy that would be useful for any kind of purpose. Any estimate in such a situation would be thrown away as soon as Google and other resources are available. Therefore they effectively cannot answer the question, and the question is useless.
v0cab 14y ago
> they'll make assumptions (and note the dangers of assumptions) So is it OK to make assumptions or not?
michaelcampbell 14y ago
> No-one is interested in the number you come up with. They're interested whether or not you have a process you use to come up with that number. Then ask, "How would you figure out how many golf balls fit in a bus?" This circuitous way around finding out what you want is anathema to most techie types anyway. My problem with these brainteaser type questions is the interviewer (in my experience) NEVER has had the experience or know-how to interpret the answer; all they have been able to do is get a level of "ah, interesting" type "gut feel" from it. If I'm interviewing with someone who's got the background to be able to analyze what I'm actually thinking, fine, but to date, I've not seen it.

Limes102 14y ago

I agree.. I would probably have left.. The questions either have subjective answers or are totally trivial.

mistercow 14y ago
How do you mean "subjective"? There is an objective answer to the question "how many golf balls can fit in a double decker bus" and while I suppose you could call it "trivial", being able to make that kind of estimate efficiently really is an important skill for programmers (and scientists, and engineers) to have. That said, this is another FizzBuzz sort of test, and should not be made unnecessarily complicated. This is what you're trying to filter out: http://www.youtube.com/watch?v=Qhm7-LEBznk http://www.youtube.com/watch?v=Qhm7-LEBznk
- v0cab 14y ago
  There's so many different kinds of buses, and it clear what kind of level of accuracy is required. I can just say 'two thousand' and that's a good enough answer. The problem is, that isn't good, as the interviewer wants to 'see how I think'. But he hasn't really given me a problem to think about, so I have to just put on a show for him. He hasn't seen how I think at all; he's just seen me putting on a show based on what I think he wants to hear.
  - mistercow 14y ago
    >There's so many different kinds of buses There is a lot of variance in bus sizes, but not enough to put you off by more than an order of magnitude. > and it clear what kind of level of accuracy is required. Knowing what kind of accuracy is required is sort of part of the test. The parameters are vaguely specified, so you should know that you're looking at orders of magnitude. >I can just say 'two thousand' and that's a good enough answer. That would fit in a large duffle bag. If you told me that you thought you could only fit 2000 golf balls in a double decker bus, I would assume that you either put zero thought into answering the question, or that you did not have a good grasp of how to estimate things. > The problem is, that isn't good, as the interviewer wants to 'see how I think'. The interviewer wants to know that you can give sane estimates based on rough calculations. As the article explains, there are many, many situations where a programmer needs to be able to do this kind of thing. It's not about "seeing how you think". It's about seeing that you can think – at all – about estimation problems. > But he hasn't really given me a problem to think about, so I have to just put on a show for him. He hasn't seen how I think at all; he's just seen me putting on a show based on what I think he wants to hear. And if that show is "2000 balls", he has learned that he should not hire you.

rodly 14y ago

Why is it a waste of time if it gets you the job? The answer is "trivially easy" so it shouldn't take you long to waste your time on. I'd wager that you spent at least twice as much time writing up your response to this article than it would take to answer such an interview question. What's the true waste of time here?

ColinWright 14y ago

Like FizzBuzz, you over-estimate people's ability to do this. I know many programmers who are able to knock out a Rails App without breaking a sweat, but ask them to think about throughput, or simultaneous connections, or machine load, or disk access, or anything else requiring ballpark estimates and general arithmetic and they're lost. Sure, I know what I'm hiring you for today, but in a small company what you're doing today won't be what you're doing next month, unless you're so limited as to be unable to think outside your own existing speciality. Ability to adapt is critical. By the time I've got you to interview I already know you can program, and most likely you've already shown an interest in my company. If you're unable to have a hack at something just because you think it's unrealistic, or poorly defined, or just uninteresting, that tells me something about you. And to be fair, and in the interests of full disclosure, before I ask these questions I ask the candidate's opinion of them. In some cases that's already enough.

mistercow 14y ago

>It's trivially easy to figure out how to calculate a rough number. I'd go so far as to say blatantly obvious. It's also a waste of time to actually do it. Given any X, only a small minority of the people who believe they have the skills needed to do X competently are right. Dunning–Kruger as usual. It should be trivially easy to figure out roughly how many golf balls fit in a double-decker bus. In fact, it shouldn't take more than a few minutes of figuring, so the time wasted ought to be minimal. If it does take longer than a few minutes, then the interviewer has learned something important about you, so it's not a waste of time then either.

deleted 14y ago

[deleted]