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I don't understand people's problem with estimating. It's a useful skill. Perhaps it would be better if the questions actually related to technology, rather tha

by Jabbles 13y ago

I don't understand people's problem with estimating. It's a useful skill. Perhaps it would be better if the questions actually related to technology, rather than golf balls - but the principle is the same. For instance - "how many hard drives does Gmail need?" requires a rough guess of how many users Gmail has (if you're interviewing at Google, you should know it's 1e8-1e9). How much space each one takes (probably nowhere near a gigabyte on average - let's say 1e8 bytes). And that the current capacity of hard drives is (1e12 bytes). Then you can say that they probably need 1e5 hard drives, link it to redundancy, availability, deduplication, backups etc. You can comment that it's feasible to build a datacenter with that many hard drives. No one cares that the actual number is 12,722 - but you've demonstrated a broad set of knowledge about the current state of technology. Saying "dunno - a billion?" is not going to get you anywhere, and with good reason. The Monopoly question is crap, though. I'd like to know how useful http://google-tale.blogspot.com/2008/07/google-billboard-puzzle.html http://google-tale.blogspot.com/2008/07/google-billboard-puz... was.

tomlu 13y ago
They do ask those sorts of questions still, but I wouldn't call them brainteasers.
- lancewiggs 13y ago
  In which case this is lifted in part out of the McKinsey interview play book. A behavioural interview and a case study, with a resume review frost up. Keeping the case studies consistent across a set of interviewees for the best calibration. Making them realistic problems rather than academic exercises or quizzes means multiple paths can be taken to a variety of right answers. Laszlo and many others inside his area are ex McKinsey. (As am I)
  - dpritchett 13y ago
    As a developer I've never heard good things about McKinsey. Can you tell us your perspective on their value proposition and the relevance of their hiring methodology? The best I've heard about them is that they provide political cover for executive agendas that might not play well absent validation from a third party with some academic credentials.
    - lancewiggs 13y ago
      McKinsey don't operate above the radar, but are responsible for helping with an incredible number of major corporate decisions across the world. Recruitment and development is McKinsey's core advantage. They attract and retain incredible talent from all sets of places. Teams work with the top clients - the CEO and team as well as high flyers at more junior levels. Things get done extraordinarily quickly. And well. But make sure that the internal team is up to scratch, and that there is that mandate from the top. There is no prescription for how to deliver a project, beyond the hypotheses approach. There is an obligation to dissent, and a client-first mandate. When enforced well the client gets what they need to hear, not want they want to hear. High quality consultants don't want to work on projects justifying dumb decisions - and can choose not to. Use McKinsey and other consultants to help with new issues, not business as usual. They are fantastic for quickly understanding and assessing important questions of strategy, for mergers and acquisitions, organisational design and so on. They help understand the context and set the new agenda, or validate the old one. Generally clients simply don't have enough internal capacity to perform this work alone. Use them, decide what to do and start doing it - and then get rid of them. Consultants that are camping at a client are in effect wildly expensive employees.
rorrr2 13y ago
The problem is, the interviewers often judge how accurate your estimation is, and not the fact that you know (the highly flawed) Drake Equation. These estimates are completely useless in real life, because in real life nobody guesses how many drives you need for GMail, or how many gas stations there are in LA.
- hkmurakami 13y ago
  In every situation I know of, it's not the accuracy of the answer that is being judged but rather the thought process and basic math and assumptions chosen to get there. In any case it's one of those things where you tend to do well if you've prepared for it and do pretty poorly if you face it for the first time. Probably a better fit for interviewing management consultants than programmers for sure though
- ig1 13y ago
  I'm not sure where you've worked, but doing resource estimation for projects has been pretty important for most greenfield projects I've worked on. It's also good for sanity testing, it's a useful skill to be able to spot that something is out by an order of magnitude as it can allow you to catch problems early on.
  - rorrr2 13y ago
    Data-backed estimation is completely different from random guesses you will make during an interview. Not only that, even if your guesses are decent, multiplying them can drive you orders of magnitude in the wrong direction.
    - ig1 13y ago
      The underlying data might be different but the process is the same, you need to figure out what are the contributing factors, how they relate and establish an upper and lower bounds for the values you're assuming. Once you have data you can make corrections to those bounds, but other than that the process is the same. It's a skill that a lot of first time startup founders lack. They have no-idea how to estimate the market size for their startup, you need to understand the process of how to build an estimation model.
pavanred 13y ago
Even if this idea had some merit, I think once the candidates start preparing for interviews by reading some idiots guide to brain teasers then it loses it purpose and further hurts the candidate who is actually skilled, quick on his feet and has good instincts.
rayiner 13y ago
I had a professor who used to say: a great engineer should be able to answer any question in 30 minutes, at some level of precision. Her example was deriving the equations for the dynamics of the space shuttle. You should be able to do it in 30 minutes, even if it's an extreme approximation.
nawitus 13y ago
>(if you're interviewing at Google, you should know it's 1e8-1e9) Why? Is the interview a trivia exam like in college?
sliverstorm 13y ago
The other nice part about being able to estimate- you can often determine feasibility with a reasonable degree of confidence, for a minimal investment in effort.
fishtoaster 13y ago
I used to think estimation questions were useful. I still think that estimation ability is something a programmer needs for exactly the reasons you state. However, I used to ask one estimation question (How many hours have you spent coding over the course of your life) on all my interviews. Over time, I lost interest in it because almost everyone got it "right" (took an acceptable route and arrived at a reasonable estimate). The only people that got it wrong were ones I decided to reject for other reasons (this being a semi-technical but mostly ask-about-experience phone interview). So, although I agree it's a useful skill, I don't think it's worth askin estimation questions from my personal experience.
bcgraham 13y ago
> Saying "dunno - a billion?" is not going to get you anywhere, and with good reason. Not sure if you were referencing this bit from comedian Pat Brice, but here's a relevant video: http://www.youtube.com/watch?v=J2nrKdECSGU http://www.youtube.com/watch?v=J2nrKdECSGU

by Jabbles 13y ago

tomlu 13y ago

They do ask those sorts of questions still, but I wouldn't call them brainteasers.

lancewiggs 13y ago
In which case this is lifted in part out of the McKinsey interview play book. A behavioural interview and a case study, with a resume review frost up. Keeping the case studies consistent across a set of interviewees for the best calibration. Making them realistic problems rather than academic exercises or quizzes means multiple paths can be taken to a variety of right answers. Laszlo and many others inside his area are ex McKinsey. (As am I)
- dpritchett 13y ago
  As a developer I've never heard good things about McKinsey. Can you tell us your perspective on their value proposition and the relevance of their hiring methodology? The best I've heard about them is that they provide political cover for executive agendas that might not play well absent validation from a third party with some academic credentials.
  - lancewiggs 13y ago
    McKinsey don't operate above the radar, but are responsible for helping with an incredible number of major corporate decisions across the world. Recruitment and development is McKinsey's core advantage. They attract and retain incredible talent from all sets of places. Teams work with the top clients - the CEO and team as well as high flyers at more junior levels. Things get done extraordinarily quickly. And well. But make sure that the internal team is up to scratch, and that there is that mandate from the top. There is no prescription for how to deliver a project, beyond the hypotheses approach. There is an obligation to dissent, and a client-first mandate. When enforced well the client gets what they need to hear, not want they want to hear. High quality consultants don't want to work on projects justifying dumb decisions - and can choose not to. Use McKinsey and other consultants to help with new issues, not business as usual. They are fantastic for quickly understanding and assessing important questions of strategy, for mergers and acquisitions, organisational design and so on. They help understand the context and set the new agenda, or validate the old one. Generally clients simply don't have enough internal capacity to perform this work alone. Use them, decide what to do and start doing it - and then get rid of them. Consultants that are camping at a client are in effect wildly expensive employees.

rorrr2 13y ago

The problem is, the interviewers often judge how accurate your estimation is, and not the fact that you know (the highly flawed) Drake Equation. These estimates are completely useless in real life, because in real life nobody guesses how many drives you need for GMail, or how many gas stations there are in LA.

hkmurakami 13y ago
In every situation I know of, it's not the accuracy of the answer that is being judged but rather the thought process and basic math and assumptions chosen to get there. In any case it's one of those things where you tend to do well if you've prepared for it and do pretty poorly if you face it for the first time. Probably a better fit for interviewing management consultants than programmers for sure though
ig1 13y ago
I'm not sure where you've worked, but doing resource estimation for projects has been pretty important for most greenfield projects I've worked on. It's also good for sanity testing, it's a useful skill to be able to spot that something is out by an order of magnitude as it can allow you to catch problems early on.
- rorrr2 13y ago
  Data-backed estimation is completely different from random guesses you will make during an interview. Not only that, even if your guesses are decent, multiplying them can drive you orders of magnitude in the wrong direction.
  - ig1 13y ago
    The underlying data might be different but the process is the same, you need to figure out what are the contributing factors, how they relate and establish an upper and lower bounds for the values you're assuming. Once you have data you can make corrections to those bounds, but other than that the process is the same. It's a skill that a lot of first time startup founders lack. They have no-idea how to estimate the market size for their startup, you need to understand the process of how to build an estimation model.

pavanred 13y ago

Even if this idea had some merit, I think once the candidates start preparing for interviews by reading some idiots guide to brain teasers then it loses it purpose and further hurts the candidate who is actually skilled, quick on his feet and has good instincts.

rayiner 13y ago

I had a professor who used to say: a great engineer should be able to answer any question in 30 minutes, at some level of precision. Her example was deriving the equations for the dynamics of the space shuttle. You should be able to do it in 30 minutes, even if it's an extreme approximation.

nawitus 13y ago

>(if you're interviewing at Google, you should know it's 1e8-1e9) Why? Is the interview a trivia exam like in college?

sliverstorm 13y ago

The other nice part about being able to estimate- you can often determine feasibility with a reasonable degree of confidence, for a minimal investment in effort.

fishtoaster 13y ago

I used to think estimation questions were useful. I still think that estimation ability is something a programmer needs for exactly the reasons you state. However, I used to ask one estimation question (How many hours have you spent coding over the course of your life) on all my interviews. Over time, I lost interest in it because almost everyone got it "right" (took an acceptable route and arrived at a reasonable estimate). The only people that got it wrong were ones I decided to reject for other reasons (this being a semi-technical but mostly ask-about-experience phone interview). So, although I agree it's a useful skill, I don't think it's worth askin estimation questions from my personal experience.

bcgraham 13y ago

> Saying "dunno - a billion?" is not going to get you anywhere, and with good reason. Not sure if you were referencing this bit from comedian Pat Brice, but here's a relevant video: http://www.youtube.com/watch?v=J2nrKdECSGU http://www.youtube.com/watch?v=J2nrKdECSGU