Facebook Data Scientist Interview Questions | Glassdoor

Facebook Data Scientist Interview Questions

Updated Oct 12, 2017
113 Interview Reviews

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Helpful (290)  

Data Scientist Interview

Anonymous Interview Candidate
No Offer
Neutral Experience
Difficult Interview

Interview

One HR interview, one takehome data challenge, one shared screen with SQL and one onsite with several 1:1 interviews. They check your coding skills and product sense via the takehome, your sql skills via the shared screen interview and machine learning theory as well as product sense during the onsite.
They let you choose the language for the takehome and onsite there is no coding on the board. So you just need to know one language (whichever you want, although I think they prefer R or Python) + SQL. No C++/Java/etc stuff and no CS algo questions.

Interview Questions

  • Data challenge was very similar to the ads analysis challenge on the book the collection of data science takehome challenge, so that was easy (if you have done your homework).

    SQL was: you have a table where you have date, user_id, song_id and count. It shows at the end of each day how many times in her history a user has listened to a given song. So count is cumulative sum.
    You have to update this on a daily basis based on a second table that records in real time when a user listens to a given song. Basically, at the end of each day, you go to this second table and pull a count of each user/song combination and then add this count to the first table that has the lifetime count.
    If it is the first time a user has listened to a given song, you won't have this pair in the lifetime table, so you have to create the pair there and then add the count of the last day.

    Onsite: lots of ads related and machine learning questions. How to build an ad model, how to test it, describe a model. I didn't do well in some of these.   20 Answers

Other Interview Reviews for Facebook

  1. Helpful (130)  

    Data Scientist Interview

    Anonymous Interview Candidate in Menlo Park, CA
    Declined Offer
    Negative Experience
    Difficult Interview

    Application

    I applied online. The process took 6 weeks. I interviewed at Facebook (Menlo Park, CA) in February 2017.

    Interview

    I applied online in late December and then spoke to a recruiter for about 15 minutes in early January. I was scheduled for an in-person interview in mid January where I interviewed with one data scientist in a 1:1 interview for an hour for the first round. Another recruiter then called me for a 30 minute prep for the 2nd round. The final, 2nd round interview was about 5 weeks later in late February, with 6 data scientists over 4 hours in the afternoon. I got an offer but it was for a lot less than I was expecting, and we couldn't bridge the gap enough for it to be worth it.

    Everyone seemed relatively nice, although I could tell that a lot of the questions are really designed to trip you up, like they want you to miss some detail or edge case. My advice would be to pay attention to every little bit of minutiae regarding the question, make sure you're staying on task, write on the whiteboard, and explain your thoughts. Industry word is that data science at Facebook is not what it once was and is more of a product data analyst role now, so make sure you're really into Facebook products because that's what you'll be analyzing.

    Also, I didn't get a single question about dice, cards, or any other brain teaser type questions. All these mentions of NDAs are missing the point of Glassdoor, people can be a little more verbose than "various questions". You can't trademark an interview question or claim it's a trade secret.

    Interview Questions

    • How would you measure the health of Mentions, Facebook's app for celebrities? How can FB determine if it's worth it to keep using it?

      If a celebrity starts to use Mentions and begins interacting with their fans more, what part of the increase can be attributed to a celebrity using Mentions, and what part is just a celebrity wanting to get more involved in fan engagement?   6 Answers
    • There is a table that tracks every time a user turns a feature on or off, with columns user_id, action ("on" or "off), date, and time.

      How many users turned the feature on today?
      How many users have ever turned the feature on?
      In a table that tracks the status of every user every day, how would you add today's data to it?   8 Answers
    • If 70% of Facebook users on iOS use Instagram, but only 35% of Facebook users on Android use Instagram, how would you investigate the discrepancy?   5 Answers
    • How do you measure newsfeed health?   2 Answers
    • If a PM says that they want to double the number of ads in Newsfeed, how would you figure out if this is a good idea or not?   3 Answers
    • We have two options for serving ads within Newsfeed:
      1 - out of every 25 stories, one will be an ad
      2 - every story has a 4% chance of being an ad

      For each option, what is the expected number of ads shown in 100 news stories?
      If we go with option 2, what is the chance a user will be shown only a single ad in 100 stories? What about no ads at all?   12 Answers
    • How do you map nicknames (Pete, Andy, Nick, Rob, etc) to real names?   3 Answers
    • Facebook sees that likes are up 10% year over year, why could this be?   4 Answers
    • How many high schools that people have listed on their profiles are real? How do we find out, and deploy at scale, a way of finding invalid schools?   4 Answers

  2.  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Positive Experience
    Average Interview

    Application

    I applied online. The process took 2 weeks. I interviewed at Facebook.

    Interview

    This was an interview for the analyst side of Facebook rather than the ML team. A recruiter reached out and discussed the interview process with me, though I did not advance beyond the phone interview stage. Following the discussion with the recruiter, a phone interview was scheduled with a Facebook data scientist. The person I interviewed with was great to speak with and well-versed in how Facebook works (answered all my questions with clear knowledge of the company).

    The interview was conducted via video and a code-sharing website. As with most Facebook interviews, there was a SQL question and a business case question. The SQL question was not as difficult as I was expecting, but I flubbed some basic maths in the process by trying to make it more complicated than it needed to be. I'm not sure if that was the sole reason I did not move forward, but I'm sure there were candidates who answered the question flawlessly.

    The business case scenario was interesting, and again I think I did reasonably well but not excellent. There were several terms that I was unfamiliar with (e.g., countermetrics) and I was quite upfront about my lack of knowledge during those parts of the interview. I am coming straight from academia and am not going to fake business knowledge. I prepared quite a bit in learning/brainstorming metrics and business case scenarios, so I'm not sure if more preparation would have helped.

    In the end, the process was clear, well-managed, and friendly. Facebook does a great job with this compared to other companies I interviewed with, so I was impressed. I was not particularly interested in the position because the side of Facebook DS I was interviewing for was the analytics side and I am much more interested in ML work - something to be aware of if you are applying.

    Interview Questions

  3.  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Neutral Experience
    Difficult Interview

    Interview

    Two rounds of 45-minute phone interview. The questions were similar to those described on Glassdoor: tell-me-about-yourself type questions, some medium-to-hard level SQL, and product sense questions. The product sense part was hard to answer, since there're few resources to prepare.

    Interview Questions

    • How would you tell whether a new feature X is beneficial or not   Answer Question

  4. Helpful (1)  

    Data Scientist Interview

    Anonymous Employee
    Accepted Offer
    Positive Experience
    Average Interview

    Application

    I applied through an employee referral. The process took 3 weeks. I interviewed at Facebook.

    Interview

    I got an internal referral and the recruiters took it from there. They were very courteous and prompt in their email responses. They sent me a long prep document that very clearly laid out what you will be tested on, along with some sample questions. The actual interview aligned closely with what was said in the prep documents.

    Interview Questions


  5. Helpful (2)  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Negative Experience
    Easy Interview

    Application

    I applied online. I interviewed at Facebook.

    Interview

    The recruiter contacted me via linkdin and set up a phone interview with one of the data scientists in facebook. It was supposed to be 45 minutes and the recruiter had already sent out a detailed email of what to expect. The interview began with a sql coding qs , followed by A/B test questions and how to track decrease/increase of metrics.
    I was able to answer each one of them but the interviewer seemed hardly interested and there were no follow up questions as if he didn't find me worthy of engaging in any conversation. My overall experience was bad and I could have cleared the interview had there been a better guy with more experience and understanding of how interviews are conducted.

    Interview Questions

    • Write a sql query to find out the overall friend acceptance rate for a given date?
      Table :- User_id_who_sent|User_id_to_whom|date|Action (Sent, accepted, rejected etc)   2 Answers
    • What would be your approach to check if the overall acceptance rate has decreased from 60% in may'17 to 30% in sep'17   1 Answer
    • How would you conduct an experiment to test if a change in facebook app is effective and what metrics will you look at?   1 Answer

  6.  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Neutral Experience
    Difficult Interview

    Interview

    Sent in resume and got contacted for a recent graduate Data Science job. The interview was in 2 rounds, lot of stats questions as well as a coding challenge.

    Interview Questions

    • Probability questions, and questions on machine learning methods   Answer Question

  7. Helpful (4)  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Negative Experience
    Easy Interview

    Application

    I applied through a recruiter. I interviewed at Facebook in September 2017.

    Interview

    This was purely technical. There were no questions about past experience, areas of interest, or personality. I was encouraged by the recruiter to be prepared to "whiteboard code" and study facebook example interviews, which I did. They want to see your face during the interview, which is a little creepy, but beyond that I thought the interview was nice. The questions were easy. I think someone who has little to no experience, but has gone through some online training could probably pass this interview. For this reason, I am not sure why I wasn't good enough to get to the next round. I felt confident in my answers and thought we had a good up-beat dialog. I've never felt so good leaving an interview to be so quickly rejected.

    Interview Questions

    • 1. Easy SQL join and aggregation (can be done in your language of choice)
      2. Discuss pros and cons of using like-rate to determine system health
      3. Discuss what might cause average like rate to go from 70% one day to 30% another
      4. Explain how you would diagnose a 10% YoY "like" improvement
      5. What would be your next step to investigating why this happened   1 Answer
  8. Helpful (1)  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Positive Experience
    Average Interview

    Application

    I applied through an employee referral. The process took 3 weeks. I interviewed at Facebook in September 2017.

    Interview

    Got scheduled through a recruiter. It takes 2-3 weeks for the interview to get scheduled. Focus A LOT on SQL or Python (mainly dictionaries and lists) depending on what what you choose.

    Interview Questions

    • There is a feature for showing friend requests. How do you measure its impact and how do you decide whether to keep it.   1 Answer
    • If revenue is down 1% and time spent is up 2%, what do you infer/ decide?   1 Answer
    • A set of values given: Assume table in SQL or list of dictionaries if using Python.
      Basically a row of data contained information:
      if it is post or it is a comment, row id and some other data.
      Find distribution of comments.
      #comments # posts
      1 5000
      2 6787
      ..
      ..   2 Answers

  9.  

    Data Scientist Interview

    Anonymous Interview Candidate
    Declined Offer
    Positive Experience

    Interview

    Great process: went smoothly, no unpleasant surprises. The questions were interesting and the interviewers were very professional. The company definitely made a good impression on me overall. The recruiters and HR know what they're doing.


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