Facebook Data Scientist Interview Questions | Glassdoor

Facebook Data Scientist Interview Questions

Updated Apr 16, 2018
140 Interview Reviews

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Helpful (330)  

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.   23 Answers

Other Interview Reviews for Facebook

  1. Helpful (196)  

    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?   7 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?   4 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?   14 Answers
    • How do you map nicknames (Pete, Andy, Nick, Rob, etc) to real names?   5 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
    Negative Experience
    Difficult Interview

    Interview

    The interview process was smooth but impersonal. The vibe at Facebook is unfriendly -- this is surprising for a company priding itself on connecting people and friends.

    The onsite has a few business case components coupled with a SQL and probability test.

    Interview Questions

  3.  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Positive Experience
    Easy Interview

    Application

    I applied through college or university. I interviewed at Facebook.

    Interview

    Initial interview was relatively simple. Just questions about what aspects of available data you would use to answer certain business questions or anomalies. One relatively complex SQL question. Should've brushed up more on my SQL! What you come to find out is that the "Data Scientist" role with Facebook is really just more of a Data Analyst type role.

    Interview Questions

    • Say you notice a surge in average activity among users but the number of users is down, how would you explain this?   2 Answers

  4.  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Neutral Experience
    Difficult Interview

    Application

    I applied in-person. The process took a week. I interviewed at Facebook in March 2018.

    Interview

    Was contacted by a Facebook recruiter and then the resume exchanged hands when finally got a call from Infrastructure team. Recruiter herself asked screening questions from sql, statistics and programming, trivial ones.

    It was followed by a phone interview. It was from 3 areas in sql, programming and machine learning. Recruiter was clearly interviewing to test the limits. There were 3 questions on sql, 1 on programming and 2 questions on machine learning concept. The focus on machine learning was quite less and primary focus seemed to be on sql and programming.

    Sql questions were on group by and joins. The first question needed a self join which i didn't get at first, but the interviewer was helpful. The other 2 questions were straight forward group by and join questions .

    programming question was a bit unexpected for doing in 20 mins. Was given a log file of format
    id, accepted, id1,id2,id3
    id, rejected, id5
    id3,request, id6

    and was asked to create a network graph from it. I guess the interviewer wanted the result in simply a dictionary , but started with what will be the best data structure to store it, to which i answered bi directional graph and then asked me to code the graph, which got me confused b/w the linked list approach and the normal dictionary approach and ended up taking more time. In midway he said that he understood my approach and moved to machine learning.

    In machine learning the questions were between bias variance trade off and PCA . In PCA he went into detail as in what method is used to decompose matrix, what is the significance of first principal component and in the end what is the relationship between the first and second principal component. I got stuck at the relationship between first and second principal component.

    I got rejected. My best guess is because of the programming question. Recruiter had suggested that phone interview will be around basic data processing question, so wasn't expecting a network graph question at the phone interview level. But guess it's facebook :)

    Interview Questions

    • To create a network graph from a log file in 20 mins. Guess the interviewer wanted a simple dictionary as a data structure but confused me with calling it a network graph repeatedly. If he indeed wanted it like a graph where all properties such as pre order , in order traversal could be applied. It's no way a 20 min question.   3 Answers

  5.  

    Data Scientist Interview

    Anonymous Interview Candidate in Boston, MA
    No Offer
    Negative Experience
    Average Interview

    Application

    I applied through a recruiter. The process took 2 weeks. I interviewed at Facebook (Boston, MA) in March 2018.

    Interview

    HR reached out to me on linkedin for data scientist infrastructure position. Scheduled an interview after 2 weeks. This was a technical round with sql, python and statistics questions. The interview lasted for an hour with live coding. The interviewer was very nice and i answered all of the questions. I was not sure about logic for one of the questions on python. Rest were right. I did not make it to the next round. I am sure what went against me but assume python was the issue.

    Interview Questions

    • A table has a column with full names(e.g. 'Tom Hardin'). write a python code to get distinct first names(i know its super easy in sql)   3 Answers

  6.  

    Data Scientist Interview

    Anonymous Interview Candidate in San Francisco, CA
    No Offer
    Negative Experience
    Easy Interview

    Application

    I applied through a staffing agency. The process took 2 weeks. I interviewed at Facebook (San Francisco, CA) in March 2018.

    Interview

    The phone interview was product sense related plus SQL question. The onsite was 4 rounds plus a break in between. They are not trying to hire experienced data scientists but some business analysts with basic stats knowledge. No questions were ask related to how you build a model or how you lead a project. They just wanted to know if you can get the conditional probability calculated correctly.... People there told me that they havent created an ML model for months. All the questions I got asked was around there pages, likes, and ads. It really shouldn't be called a data scientist position.

    Interview Questions

    • WHat's the probability of something, what's the distribution of sth   1 Answer

  7.  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Neutral Experience
    Difficult Interview

    Application

    I applied through an employee referral. The process took 4 weeks. I interviewed at Facebook.

    Interview

    One call with the recruiter and one phone interview with a Data Scientist and moved on to on-site interview with 5 rounds of interviews. In the phone interview, it's mostly brainstorming metrics and an SQL query question. The 5 rounds of on-site interviews includes 2 SQL, 2 A/B testing and 1 Math interviews.

    Interview Questions

    • If there's a new feature that attracts more pop stars to use it, how do you evaluate whether this feature is successful or not?   Answer Question
  8. Helpful (2)  

    Data Scientist Interview

    Anonymous Interview Candidate
    No Offer
    Negative Experience
    Difficult Interview

    Application

    I applied through a recruiter. The process took 4+ weeks. I interviewed at Facebook in February 2018.

    Interview

    Was first approached by an internal recruiter at Facebook via a LinkedIn message. Within a week I did an initial 15 minute screening interview in which the recruiter asked me if I had experience/competence in SQL, Python, or R.

    Afterwards I was sent around 2-3 emails containing study material, along with advice on how to prepare for a 1-on-1 video interview I was to have. After I reviewed the material I was to schedule a time to interview with a Data Scientist Manager.

    The interview was a mix of analytical problem solving and technical. It was enjoyable getting to interact with someone very talented in their skills and showcased Facebook's level of talent well. During the interview there was a degree of guidance as I navigated the technical components and analytical portion of the interview, which was expected per the interview prep material.

    Personal Analysis of Interview:
    It was great getting to be challenged both technically and analytically from the top talent around, and felt that I showcased my problem solving capabilities well but undersold my technical skills. Not sure I would have done any studying differently, I am just not at the technical level that is required at a company like Facebook.

    However, it has been nearly a month since my interview and haven't received any communication from the HR department despite multiple (3) follow up emails on my behalf. Very disappointing, as I had a wonderful experience leading up to that. This experience has definitely soured the experience and desire to work at Facebook. Hopefully this is an isolated case.

    Interview Questions

    • Suppose the Recommended Friends team has updated the algorithm to analyze if the new algorithm is better than the old algorithm.   1 Answer
    • Given the following tables how would you know who has the most friends

      REQUESTS
      date | sender_id | accepter_id

      ACCEPTED
      accepted_at | accepter_id | sender_id   6 Answers

  9. Helpful (1)  

    Data Scientist Interview

    Anonymous Interview Candidate in Menlo Park, CA
    No Offer
    Positive Experience
    Average Interview

    Application

    I applied through a recruiter. The process took 4+ weeks. I interviewed at Facebook (Menlo Park, CA) in January 2018.

    Interview

    I was contacted by the recruiter with whom I had a brief 10-15 minute phone call. Then we went ahead with a virtual interview with another data scientist. The online interview consisted of writing code in a text editor answering some data analysis questions such as how do you measure user engagement, how do you measure the effectiveness of a new feature. The interviewer was looking more for the thought process than actual execution of the code.

    I got through the online interview and was scheduled for the onsite interview loop consisted of five interviews of 30 minutes each. Two required product analytics brainstorming, one was statistics and probability, and two more were performing ETL using SQL and also performing analysis using SQL. There was a lunch break of an hour in between.

    I had a great experience throughout the interview process and the recruiter helps out a lot by emailing preparation materials and calling to discuss the material. Unfortunately I did not get through the last interview. I was not given a reason, just that there were many applicants.

    Interview Questions

    • How do you calculate monthly active users, churned users and resurrected users from a user activity log with userID and DateTime   2 Answers

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