Facebook data scientist interview: the only post you'll need to read

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Data scientist interviews at Facebook are really challenging. The questions are difficult, specific to Facebook, and cover a wide range of topics.

The good news is that the right preparation can help you maximize your chances of landing a job offer, and we've put together the ultimate guide below to help you succeed.

Here's an overview of what we'll cover:

1. Interview process and timeline

1.1 What interviews to expect

What's the Facebook data scientist interview process and timeline? It typically takes four to eight weeks and follows these steps:

  1. Application and referrals
  2. Recruiter call (~15 min). 
  3. Tech interviews (1-2 interviews, 45min each). 
  4. Onsite interviews (4 interviews, 30min each).

    Let's look at each of these steps in more detail below:

    1.1.1 Application and referrals

    Step one is getting a Facebook interview in the first place. In this guide we're focusing primarily on the interviews, so we'll keep this portion brief. You can apply to Facebook directly or a recruiter may reach out to you via LinkedIn. In either case, it helps to have a quality (and up-to-date) resume that is tailored to data scientist positions, and to Facebook more specifically. 

    It can also be helpful to get an employee referral to the Facebook recruiting team internally. This may not be possible, but if you do have a connection to someone who works at Facebook, then this can help you get your foot in the door for an interview.

    1.1.2 Recruiter phone screen

    In most cases, you'll start your interview process with Facebook by talking to an HR recruiter on the phone. But don't underestimate this initial interview. Although for many roles the initial phone screen is used to ask basic resume and behavioral interview questions, for Facebook data scientists it often includes SQL and product analysis questions. So make sure you're ready from the beginning.

    If you get past this first HR screen, the recruiter will then help you schedule the next round. One great thing about Facebook is that they are very transparent about their recruiting process. And once you've been invited to the next round, they will likely give you some additional information about what to expect in their interview process.

    1.1.3 Technical screen

    The typical process is to just have one technical screen and then to advance to the onsite interviews. However, in some cases, candidates will have two technical screens before receiving their offer decision (i.e. there would be no onsite interviews in this case). If you're not sure which process applies to your role and location, then just wait and you should find out after you pass the recruiter phone screen.

    The types of questions you'll be asked during the technical interview(s) are similar to the questions you'll encounter during the onsite interviews (see below). In particular, be prepared to answer SQL and analysis case questions. To prepare for these, get some practice with the question examples in section 2 below and also see the preparation tips in section 3.

    1.1.4 Onsite interviews

    The final stage in the interview process for Facebook's data scientist candidates, is the onsite interviews. As outlined by Facebook's very useful onsite prep guide, the onsite typically includes 4 interviews of 30 minutes, consisting of:

    1. Analysis case: product interpretation. This is a product case study which focuses on how you translate user behaviour into ideas and insights using data and metrics. 
    2. Analysis case: applied data. Here you'll get a bit more technical, focusing on how to solve a product-related problem using data.
    3. Quantitative analysis, where you'll face quantitative reasoning questions that test your knowledge of relevant mathematical, statistical and probabilistic concepts, along with applied statistics questions that will see if you can apply these concepts to real-world problems.
    4. Technical analysis. This is a coding interview where you'll analyze an open-ended product problem and try to solve it through code.

    You'll need to work through your solutions on a whiteboard, or the online equivalent if you're not there in person. It's also worth mentioning that the questions you're asked in the onsite interviews tend to be more difficult than the questions from the technical round. So, be sure to double down on your preparation for them!

    [COVID note] It's likely that your onsite interviews will be held virtually instead of in-person, given the COVID-19 pandemic. However, your recruiter should be able to provide you the most up-to-date information on Facebook's onsite interview procedures. Feel free to ask your Facebook recruiter for details, just wait until you've been officially invited to participate in the onsite interviews.

    1.2 What happens behind the scenes
     
    Throughout the interview process at Facebook, the recruiter usually plays the role of "facilitator" and moves the process from one stage to the next. Here's an overview of what typically happens behind the scenes:
    • After the technical interview, the interviewer(s) you've talked to submit their ratings and notes to the internal system. Your recruiter then reviews the feedback, and decides to move you to the onsite interviews or not depending on how well you've done.
    • After the onsite, the interviewers will make a recommendation on hiring you or not and the recruiter compiles your "packet" (interview feedback, resume, referrals, etc.). If they think you can get the job, they will present your case at the next candidate review meeting.
    • Candidate review meetings are used to assess all candidates who have recently finished their interview loops and are close to getting an offer. Your packet will be analyzed and possible concerns will be discussed. Your interviewers are invited to join your candidate review meeting, but will usually only attend if there's a strong disagreement in the grades you received (e.g. 2 no hires, 3 hires).  At the end of the candidate review meeting, a hire / no hire recommendation is made for consideration by the hiring committee.
    • The hiring committee includes senior leaders from across Facebook. This step is usually a formality and the committee follows the recommendation of the candidate review meeting. The main focus is on fine-tuning the exact level and therefore the compensation you will be offered.
    It's also important to note that hiring managers and people who refer you have little influence on the overall process. They can help you get an interview at the beginning, but that's about it.

    2. Example questions

    Now we've covered the process, let's get into the type of questions you can expect for each type of interview. Bear in mind that the technical screen draws from the same questions types as the onsite interviews, just in less depth.

    In the below sub-sections,  we've also compiled a selection of real Facebook data scientist interview questions, according to data from Glassdoor. These are great example questions that you can use to start practicing for your interviews.

    2.1 Analysis case: product interpretation questions

    At the end of the day, Facebook's data scientists help to drive product and business decisions. They need to be able to understand problems from a range of perspectives, stepping back from the data to consider how features and metrics will affect the user experience.

    With that in mind, the first of the two analysis case interviews - product interpretation-  will ask you to think a bit more like a product owner. 

    Facebook describe this interview as "a product case study focused on interpretation of user behavior using data and metrics." You'll be asked to analyze Facebook products, discuss how they could be improved and explain how you would measure this improvement, or react to metric changes.

    Let's take a look at some questions.

    Facebook data scientist interview question examples - Analysis case: product interpretation
    • What's your favorite Facebook product and how we can improve it?
    • What Facebook products are you familiar with?
    • How would you measure the success of a product?
    • What KPIs would you use to measure the success of the newsfeed?
    • Which functionalities would be helpful in the creation of reactions on Facebook?
    • How would you improve notifications?
    • Activity in Facebook user groups is down by 20%, what do you do?
    • Friends acceptance rate decreases 15% after a new notifications system is launched - how would you investigate?

    2.2 Analysis case: applied data questions

    For the second case study interview - applied data - you'll be given a more specific product-related problem and asked to come up with an approach to solving it using a dataset that the interviewer will provide.

    On top of the data analysis you'll need to consider how to frame the problem, what metrics to use, a/b testing, technical trade-offs, etc. 

    Let's take a look at some example questions.

    Facebook data scientist interview question examples - Analysis case: applied data 
    • How would you use data to confirm that users’ high school data is real? (solution)
    • How would you evaluate the impact for teenagers when their parents join Facebook?
    • How would you decide to launch or not if engagement within a specific cohort decreased while all the rest increased?
    • How would you set up an experiment to understand feature change in Instagram stories?
    • How would you predict churn rate?
    • Given a table of data, how would you create a model to detect spam?
    • How would you create a model to find bad sellers on marketplace? How can you tell if your model is working?

    2.3 Quantitative analysis questions

    Data scientists at Facebook need to have a deep knowledge of statistics and be able to apply it to business problems. 

    With this in mind, quantitative reasoning questions will test you on mathematical, statistical and probabilistic concepts and your ability to use them in a business scenario.

    Then the applied statistics section focuses more on using stats to solve real-world data problems. Prior to your interviews you should take some time to brush up on statistics fundamentals and to practice giving concise explanations of statistical terms (e.g. p-value, recall, etc.). In addition, it's pretty common to get questions related to A/B testing, so if you have experience using A/B tests, we'd recommend preparing a specific example in advance.

    It's worth noting that Facebook says you won't face any specific machine learning questions but if you have the relevant knowledge, you can weave it into your answer to deepen the discussion.

    Let's take a look at some questions. 

    Facebook data scientist interview question examples - Quantitative analysis

     

    Quantitative reasoning

    • How do you explain p-value to non-technician?
    • What is Recall metric? Can you explain it from scratch?
    • What is R squared? Can it take negative values?
    • Explain Bayes' theorem
    • Explain hypothesis testing
    • What is a Z-test? When would you use a Z test over a T test?
     Applied statistics
    • How would you predict Samsung phone sales?
    • How many orders of Fries does McDonald's sell in a year?
    • Explain your process for doing A/B testing

    2.4 Technical analysis questions

    Facebook data scientists work with one of the strongest data sets in the world. They are expected to have fluency in SQL (or equivalent) and in this interview you can expect mainly SQL-related problems.

    You will be expected to work through your answers on a whiteboard (or online equivalent) and you should be well prepared to write SQL queries (with proper syntax).
     
    In addition to SQL questions, you should also be ready for questions related to data structures, and algorithms, although these questions are less frequently asked (data scientists tend to have fewer engineering responsibilities at Facebook than they do at other companies).

    Right, let's look at some questions.

    Facebook data scientist interview question examples - Technical analysis

     

    SQL

    • Provided a table with user_id and the dates they visited the platform, find the top 100 users with the longest continuous streak of visiting the platform as of yesterday.
    • Provided a table with page_id, event timestamp, and an on/off status flag, find the number of pages that are currently on.
    • Given a database of posts and a database of comments on those posts, how do you determine how many conversations are happening in the comments per post on average?
    • You're given two tables. One contains the date, post_id, relationship (e.g. friend, group, page), and interaction (e.g. like, share, etc.). The second table contains post_id, and the ID of the person who posted. How many likes were made on friend posts yesterday?
    • What's the difference between a left join, a union, and a right join?
    Data structure and algorithms
    • There is an algorithm that rates posts on their likelihood to be spam. how would you check if the algorithm works?
    • Given a list, search for consecutive numbers (n) whose sum is equal to a specific number (x).
    • Given a list of people with things that they own, find the people who have common items and what they are.
    • Can you find the first date of log on for a platform, given a list of users?
    • How do you revert a string?

      2.5 Behavioral questions

      In addition to the question types outlined above, you can also expect to be asked some behavioral or "resume" questions about your past work experience and your motivation for applying to Facebook. Indirectly, these questions also evaluate your communication skills. 

      Behavioral questions are a great opportunity to tell your story (in a concise way), and to demonstrate your alignment with Facebook's values and culture. If you're applying directly to a job posting, you can also be strategic by aligning your answers for behavioral questions with the top qualifications that are listed in the job description. 

      Let's see some examples.

      Facebook data scientist interview questions - Behavioral
      • Why Facebook?
      • Why data science?
      • What do you do currently?
      • Describe a data and analytics project you've worked on
      • Tell us about your past experience, skills and interests
      • What is your biggest weakness?
      • What has been the biggest challenge you have taken on?

      3. How to prepare

      Now that you know what questions to expect, let's focus on how to prepare. Below is our four-step prep plan for Facebook. If you're preparing for more companies than just Facebook, then check our generic data science interview preparation guide.

      3.1 Learn about Facebook's culture

      Most candidates fail to do this. But before investing a ton of time preparing for an interview at Facebook, you should make sure it's actually the right company for you.

      Facebook is prestigious and so it's tempting to assume that you should apply, without considering things more carefully. But, it's important to remember that the prestige of a job (by itself) won't make you happy in your day-to-day work. It's the type of work and the people you work with that will.

      If you know data scientists, engineers, or PMs who work at Facebook (or used to) it's a good idea to talk to them to understand what the culture is like. In addition, we would recommend reading about Facebook's 5 core values and hacker culture.

      3.2 Practice by yourself

      As mentioned above, you'll encounter five main types of questions at Facebook: product interpretation, applied data, quantitative analysis, technical analysis, and behavioral. One of the most useful resources around comes straight from Facebook themselves - they made a prep video with mock interviews for all four onsite rounds. You should watch it all, but for ease of reference, the timings are:

      01:56: Applied data
      12:15: Product interpretation
      27:32 Technical analysis
      44:15 Quantitative analysis

      For the analysis case interviews (product interpretation and applied data),  study our articles on how to crack product improvement questions and metric questions. We created these guides for product managers but you should find a lot of the content pretty helpful. We also recommend reading up on Facebook's products, as it will help to be familiar with how they work.

      For quantitative analysis questions, we'd recommend brushing up on statistics fundamentals. Brilliant.org offers online courses designed around statistical probability and other useful topics, some of which are free. Search for specific questions and answers around statistics, machine learning, data analysis, and others on StackExchange.

      For the technical analysis questions, your biggest priority should be to practice with example questions, especially the  SQL questions. To help with that, we'd recommend reading this analysis of the 3 "types" of SQL problems.

      For behavioral questions, we recommend learning our step-by-step method for answering behavioral questions. You can then use that method to practice answering the example behavioral questions provided in section 2.5 above.

      Finally, a great way to practice all of these different types of questions is to interview yourself out loud. This may sound strange, but it will significantly improve the way you communicate your answers during an interview. Play the role of both the candidate and the interviewer, asking questions and answering them, just like two people would in an interview. Trust us, it works.

      3.3 Practice with peers

      Practicing by yourself will only take you so far. One of the main challenges of data scientist interviews at Facebook, is communicating your different answers in a way that's easy to understand.

      As a result, we strongly recommend practicing with a peer interviewing you. If possible, a great place to start is to practice with friends. This can be especially helpful if your friend has experience with data scientist interviews, or is at least familiar with the process. You can also find peers to practice with on our mock interview platform.

      3.4 Practice with ex-interviewers

      Practicing with peers can be a great help, and it's usually free. But at some point, you'll start noticing that the feedback you are getting from peers isn't helping you that much anymore. Once you reach that stage, we recommend practicing with ex-interviewers from top tech companies.

      If you know a data scientist or someone who has experience running interviews at Facebook or another big tech company, then that's fantastic. But for most of us, it's tough to find the right connections to make this happen. And it might also be difficult to practice multiple hours with that person unless you know them really well.

      Here's the good news. We've already made the connections for you. We’ve created a coaching service where you can practice 1-on-1 with ex-interviewers from Facebook and other leading tech companies. Learn more and start scheduling sessions today.
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      Any questions about Facebook data scientist interviews?

      If you have any questions about Facebook data scientist interviews, do not hesitate to ask them in the comments below. All questions are good questions, so go ahead!