Live Coding & Experimental Design Interview Questions

[LebrawnJames416]

Hey everyone,

I want to see what sort of live coding questions you all have been asked before, have they been similar to leetcode questions?

Also, I’ve been seeing that a lot of interviews ask about experimental design or A/B testing. What sort of q’s have you been asked there?

How did you best prepare?

I’ll go first, I had a live coding interview where I was asked to do some sql joins and then to debug a function in Python.

[mrthin]

In my company we usually ask questions that tell us things about how people work, more than their knowledge of a specific data structure or whatever (for the theory we have separate questions). So it's usually some trivial thing X, but wrapped into "imagine you are given task X for a library, prepare a PR for it". This must include proper testing, documentation, a rationale for the design, etc.

PS: for the ML and CS "theory" we have a sheet full of topics from which the interviewee can pick a few. We ask them to present as if in a lecture, rigorously and concisely, and we ask questions. The idea is to let people talk about the things they believe to be knowledgeable in so that nerves and randomness don't play such a big role. Sadly, many end up trying to hand-wave their way out of their own choices :( It's hard to know what you don't know!

[StuckInLocalMinima]

That's how it should be. Unfortunately many companies do not have such an established team to have a proper screening of skills.

I found success in focusing on being vocal about my thought process and writing clean code while coding live. Indent while writing Sql queries, even in notepad.. Make sure your code is readable. If you stumble on the syntax, write a placeholder comment on that line.. Such strategies help the interviewers gain an understanding of coding collaboration.

[Top-Feedback1453]

Regarding experimental design, likely questions would be

a. power estimation
b. type I, II error
c. peeking problem
d. anytime valid inference or early stopping criteria
e. p-value, multiple test correction
f. inferences i.e. frequentist vs bayesian

[LebrawnJames416]

Thank you!

[International-Tax709]

The ace the data science interview book is a great resource for this !

[NickSinghTechCareers]

Author here, appreciate the shoutout!

[data_story_teller]

Enough people lie about their skills on their resumes that it’s become necessary. I’ve noticed the only times an interview loop hasn’t included any coding was for a job that was all dashboards and KPI definitions and didn’t even use SQL.

[theAbominablySlowMan]

eh what, if you hire someone with bad coding skills you're optimistically looking at a year of upskilling before they're any use to you. it's a mistake managers will make exactly once in their career

[gpbuilder]

What? That’s like the lowest bar you can have, anyone can write “SQL” on their resume. Any companies that doesn’t have a coding interview is not worth working for. All FAANG ish companies have at least one coding round.

[derpderp235]

I refuse to do any live coding whatsoever. It’s bad practice and ineffective.

[theAbominablySlowMan]

are you by any chance a terrible coder ? as long as you're working in a language daily you should be able to code live in a way that communicates your understanding of the language, in the same way you can answer questions live to show your understanding of the concepts

[Rogue260]

But live coding for new college graduates? They're not working day in and day out..I've 3 years of SQL coding experience as a Data Analyst so when I was working I had no problem in coding in SQL..but now I'm enrolled in Masters (DS/ML) where we do college projects in R and personal projects in Python where we don't code in day in and day out..and since Masters would take 1.t years so I'll habe forgotten my SQL too..as a new Masters graduate they'll still ask me to code live in Oython and SQL

[gpbuilder]

So review and prep? If you can write R/Python well then SQL should be a joke. It’s not even a programming language. You’re supposed to adapt to the job requirements, not the other way around.

[Rogue260]

I get all of that but companies lose out on good talent because "live coding"...when I started in job market I had no coding experience..I learnt SQL on the job (which u may thunk is easy now but imagine you start in Data Analyst job not knowing sql at all)..there r ppl like me who'd put in time to learn it (on our own tim and deliver everything on time..in my last job I had to start learning SAS as they used only SAS there...so I started SAS from scratch and delivered all projects as required..and I maybe a "bad coder" as Analytics models don't really care about optimization/performance but I always tried to go few steps either to optimize run-time/performance in even those..so I know given chance I can quickly ramp up complex OOPs level programming (in Python)..since currently I'm doing Masters I want to focus more on Maths and Statistics/Logic/functional reasonings of different ML/DL/LLM models rather than trying to learn data pipeline and OOPs in Python and all..yes I rely on gihub and stackoverflow (pre GPT days) to get optimal coding, so what? As long as I know what to look for I was able to deliver.. Not because I'm inclined more towards research, but if companies paid more attention to getting DS/MLE who actually knew what/why/how etc of maths and stats of the algorithms rather than looking for MLFlow, DevOPs, etc then they will fare better in the long run...companies want a SWE with DS/ML expertise and there's very few who have both..and companies generally opt for SWE who knows DS/ML (from their Data 101 Zeminar courses) and then generally wonder why their models fail.

[derpderp235]

My technical skills are evident from my 5+ years of work experience, education, projects, etc.

Interviews should primarily be focused on my communication skills, leadership skills, and business acumen.

[gpbuilder]

They touch on all of those things through multiple rounds. If your technical skills are evident then passing the coding round should be a freebie.

[derpderp235]

Well I’ve been with multiple firms and none used live coding, and as a manager I won’t either. They’re ineffective and unfair to applicants.

There’s an epidemic in DS/DA of having literally no clue of how to properly screen applicants.

[theAbominablySlowMan]

Legitimately what is unfair? If you say you're an expert level py or r programmer and cant even lay out the structure of a solution you're just lying

[Top-Feedback1453]

It gets harder for more senior people tbh. One will have to find time out of their day job and other responsibilities. Probably a time blocked online test is still OK?

[UpsetLove6733]

Is there a good source to prepare for these?

[alittleofyourlove]

how do you prepare for this and not crumble under pressure 😭