Facebook Data Scientist Interview Questions | Glassdoor

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Facebook Data Scientist Interview Questions

Updated Jan 17, 2018
125 Interview Reviews

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Helpful (311)  

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.   21 Answers

Other Interview Reviews for Facebook

  1. Helpful (159)  

    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?   9 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?   6 Answers
    • How do you measure newsfeed health?   3 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?   6 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 through a recruiter. I interviewed at Facebook.

    Interview

    The interview started with live coding exercises. Some technical questions were asked about statistical concepts. The next part was product development questions. Finally, it ended with questions about experimental design.

    Interview Questions

    • How would you explain a confidence interval to a non-technical audience?   Answer Question
  3.  

    Data Scientist Interview

    Anonymous Interview Candidate in San Francisco, CA
    No Offer
    Positive Experience
    Average Interview

    Application

    I applied through a recruiter. The process took a week. I interviewed at Facebook (San Francisco, CA) in December 2017.

    Interview

    I had two phone interviews with the recruiter. She was very nice, informative and helped me set up for success. I had to pull out after that due to other offer.

    Interview Questions

    • Common statistical and python related questions.
      1) How do you proof that males are on average taller than females by knowing just gender or height.
      2) What is a monkey patch
      3) How do you get the count of each letter in a sentence   1 Answer

  4. Helpful (3)  

    Data Scientist Interview

    Anonymous Employee in Palo Alto, CA
    Accepted Offer
    Positive Experience
    Average Interview

    Application

    I applied through a recruiter. The process took 2+ months. I interviewed at Facebook (Palo Alto, CA) in November 2017.

    Interview

    Very similar to what others have mentioned.

    -first call with recruiter, mainly going over your resume and having them explain the process. Afterwards he sent over prep material for the phone interviews and onsite interview. The material is really comprehensive and probably somewhat overkill, but if you review it all you will be prepared. The recruiter really really wants you to feel prepared as well, so use them as a resource! That was what stood out the most to me in the process, more than anywhere else they want you to feel ready.

    -phone interview with shared screen coding with a data scientist. Basic sql, coding, and stats questions.

    -another phone interview, very similar to the first.

    -on site interview with a mix of open ended data science problems, coding questions, sql questions, behavioral questions

    -follow up phone interview with only one subject that they felt they didn't ask enough about at the onsite

    Interview Questions

    • Tell me about a time when you received constructive criticism and how you handled it.   2 Answers

  5. Helpful (2)  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Positive Experience
    Average Interview

    Application

    I applied through college or university. The process took 4+ weeks. I interviewed at Facebook.

    Interview

    It was a 45-min technical interview. The interviewee was navigating me to give him the answer he was looking for. I answered the questions on a white board. I was asked statistics questions but with a Facebook product story behind it. I was asked to write a script that reads a file and then stores project names and people who are assigned to it.

    Interview Questions

    • Bias-variance trade-off for linear regression versus nonlinear fits   Answer Question

  6. Helpful (2)  

    Data Scientist Interview

    Anonymous Employee in Menlo Park, CA
    Accepted Offer
    Positive Experience
    Average Interview

    Application

    I applied through a recruiter. The process took 4 weeks. I interviewed at Facebook (Menlo Park, CA).

    Interview

    Recruiter reached out on Linkedin, initial 15 min phone chat to understand the role, 45 min vchat first round interview with a data scientist on the team, then five 30 min interviews onsite. I communicated with quite a few recruiters as they seem to handle different steps in the interview process, they also sent very exhaustive emails for both rounds of interview for preparation. There's another 30 min call right before the onsite with a data scientist on the team as a chance for you to ask what to expect. Interview schedule was pretty flexible; waited for less than a week to hear back after the onsite.

    The onsite interview itself wasn't that difficult! I'm giving it an "Average", but I'd say it's really on the "Easy" side if you studied the emails the recruiters sent you and the Glassdoor interview questions.

    Specifically, the interactions with my recruiter were very positive. He was very informative, helpful, timely, and professional.

    Interview Questions

    • Some SQL questions with fake tables. It was kind of tricky to wrap my head around it as white boarding was quite different from writing code on your computer screen.   Answer Question

  7.  

    Data Scientist Interview

    Anonymous Interview Candidate in Menlo Park, CA
    Declined Offer
    Positive Experience
    Average Interview

    Application

    I applied online. The process took 4 weeks. I interviewed at Facebook (Menlo Park, CA) in November 2017.

    Interview

    Got contacted by a recruiter, who initially told me to consider Data Science Manager position. The first interview was with the Recruiter, who was going over my background, and, specifically leadership skills. Next day I've got an email that due to the headcount, they can not offer me this position this year, but can consider for a Data Scientist position. The interview process was supposed to be two virtual over the web (Analytical and Technical (SQL or Python or R - my choice)), followed by an on-site interview in Menlo Park (Statistical with a choice of R or Python as a tool)

    Interview Questions

    • how do you solve business questions?   2 Answers
  8.  

    Data Scientist Interview

    Anonymous Employee in Menlo Park, CA
    Accepted Offer
    Positive Experience
    Average Interview

    Application

    I applied through other source. The process took a week. I interviewed at Facebook (Menlo Park, CA) in November 2017.

    Interview

    I came in through the Insight Data Science program. The phone screen was 45 min with some easy probability, SQL and a quick product-dive that we ran out of time on. Onsite was 4 half-hour technical interviews back to back. Everyone was engaged and thoughtful and I thought that the questions were fair. Had one hiccup misinterpreting one of the probability questions (due to ambiguous wording I thought that I was supposed to answer a much more complicated question than what was posed). Probably wasted at 10 min before we uncovered the miscommunication.

    Interview Questions

    • Some medium difficulty SQL and probability questions. Some problem-solving/modeling deep-dives   Answer Question

  9.  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Positive Experience
    Average Interview

    Application

    I applied through college or university. The process took 4 weeks. I interviewed at Facebook in November 2017.

    Interview

    The process starts with a 15 minute call with the recruiter that covers basic questions about your background and level of interest. It's nearly impossible to mess up this step. My recruiter was incredibly kind and courteous. The following interview is an ~1 hour video conference with a coding (SQL, Python, or R) question and analysis question focused on a proposed change to one of their products. This interview is conducted by a data scientist. Mine arrived late, wasn't very nice, and was kind of condescending. It seemed like they thought this was a waste of their time. I failed this interview step most likely because I don't have the requisite experience in defining KPIs. In all honesty, this position seems more like a "data analyst" position that they relabelled "scientist" in order to attract more applicants. In the analytics team, it seems like they are only performing descriptive and inferential statistics--not building predictive models. The next step would have been an on-site interview had I made it.

    Interview Questions

    • Given an event-level table of interactions between pairs of users (note that there aren't duplicates in one day for one pair of users), for each possible number of "people interacted with" find the count for that group in a given day (i.e. 10 people interacted with only one person, 20 with 2, etc.).   2 Answers

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