Facebook Data Scientist Mock Interview - Segment Influencers

This is a 30-minute mock interview based on a phone screen of a product data science role on Facebook. The interview was conducted by an Ex-PayPal data scientist who currently works in FAANG.

Parts:
0:00 Statistics Questions
9:50 SQL Questions
20:00 Case Questions

#datascience #machinelearning #dsinterview

[nanfengbb]

This is by far the best DS mock interview I have seen on youtube, in terms of the authenticity of the coding environment, interview structure/flow/time control and interaction between the interviewee and interviewer. Thank you for making this! It would be great if you can provide feedback/comments to the interviewee at the end so we can learn what areas she did great/where she can further improve. The interviewee is amazing too! I am curious, what is her experience (YOE and job title)? Thanks.

[DrEhrfurchtgebietend]

Watching her struggle with a simple SQL question really made me feel better

[MegaAntimason]

The first sql answer is incorrect you cant filter on rank yet, you have to create a sub query.

[tamabebe]

Hello, I don't know why people are being so cold, you did great on the interview.

[torinojuve]

Hi - was a Facebook DS and I gave many interviews. This is nothing like the Facebook DS interview.

[junyanyao]

The case study probably want to follow this structure: 1. why you want to distinguish influencer account ? [let's see it's for better target ads, or use these informations in recommender system, etc] 2. What kind of data are available to us (account contextual information and behavioral information)? 3. Clarify which features that can be helpful (can talk about some classification models here, but mainly should be features insights) 4. clarify which features are most important (from product sense and machine learning points- e.g. permutation importance, gini importance) 5. Summarize it.

[brothermalcolm]

I feel like this is not the typical fb style interview, but I definitely learned something useful here!

[datahat]

The case study has been worked in detail. An additional important feature could be if there any other influencers following the particular user under consideration

[reanschwarzer]

The third question about the confidence interval of logistic regression is kind of misleading and challenge from the interviewee's perspective. More clarification work should help to understand like if it is the logit format or probability format. First, the question is asking if log-odds (logit) could be 0, I think it is possible, log(p/1-p) definitely could be zero when p=1-p, then you jumped to the confidence interval of the odds ratio, which is kind of tricky if you are treating the odds ratio and log odds as the same stuff (odds ratio is not taking log). The odds ratio format should be like the exp(beta), then when 1 included in the CI, that means beta could be zero since exp(0)=1, then accept the null hp to say beta coefficient is not significant.

[AniltonNeto]

13:04 is bad, cuz the result for the division is undefined, in this case, you change NULLIF(field, 1) instead :-P and filter zero values :)

[toshb]

3:15 - isn’t (X’X)^(-1)X’y derived from the maximum likelihood estimate? I thought the correct answer would be stochastic gradient descent.

[ajitkirpekar]

Thank god it wasn't expected to derrive the MLE. Also, I am a bit surprised FB expects someone to remember the OLS matrix equations for beta coefficients. I mean, it was lasered into my brain sure, but I am not sure that's proof of anything other than I happened to commit it to memory. I also happened to commit the equations for generalized method of moments, but that's also not proof of anything.

[PremiumTrackerSilverStacker]

I don't think she answered the question right on the log odds correctly. CI in log odds is insignificant if it includes 0. CI for odds is insignificant for including 1

[chemtech]

I have never been asked these type of statistics questions or to derive formulas or coefficients on a data science interview.

[jlhi]

... a friend of mine was asked to write an algorithm for search autofill during the case portion of their interview

[vnpikachu]

The first sql you have to create a subquery, or use HAVING instead of WHERE.

[ni]

Hey the font size is too small, can you please post the questions somewhere?

[bcws]

Isn' the Beta of the logistic regression the change in Y (or log odds in this case) given a 1 unit change in X?

If so, then it is possible for Beta to be 0 (or 0 to be in beta's confidence interval) as that implies a 1 unit change in x does not have any change in log odds. However, if we want to look at odds, then we need to take the exponential of Beta, in which case it is not possible for the confidence interval of exponential of Beta to contain 0.

The confidence interval here is not referring to the log odds, but the change in log odds given a change in x.

[simonhafner]

Thanks a lot for sharing? May I ask which level this mock interview is meant for?

[techsavy]

What was the experience in years for interviewer & interviewee ?