How To Crack Spotify Data Science Technical Screen Interview

List of exact Python/SQL commands and experimentation topics you should know to nail Spotify Tech Screen

If you are preparing for Technical Screen or Technical Interview at Spotify then most likely you are looking for answers to the following questions:

How can I start preparing for Spotify Data Science tech interview?
What can I expect from Spotify Data Science tech interview?

This article will cover the following topics:

- Tech Screen Duration
- Part 1: Python Question
- Part 2: SQL Question
- Part 3: A/B Testing Question

Tech Screen Duration

This technical interview takes about 45 minutes and is divided into three parts: Python, SQL, and Experimentation.

Image Source: cottonbro

Part 1: Python Question

The first tech screen question is usually a data wrangling or data transformation question which you should do in Python, although you can do it in SQL too. This question aims to find out whether you can make use of some basic concepts such as filtering and aggregation in Python. Whether you can make use of the two most popular libraries: Pandas and NumPy.

Example Question

How to fix a bug in the data where a specific device’s data is halved for some reason?

Learn the basic functionalities in Pandas such as grouping, summing, averaging, filtering (with single and multiple values) such as:

df.groupby(“x”)
df.groupby(“x”)[“y”].sum()
df.groupby(“x”)[“y”].avg()
df[df[“x”] == k]
df[df.x.isin([k,l])]

Learn the basic filtering function in Numpy:

df[“new_vb”] = np.where(condition, value if condition true, value if condition false)

Part 2: SQL Question

The second question on the tech screen is a coding question in SQL where you need to know the basic SQL functions to filter the data, to perform joins between the two data while knowing the concept of A/B testing in depth.

To solve this problem you will need to be familiar with the basic concepts behind A/B testing such as control vs experimental groups, selecting primary success or performance metrics, and calculating it per each of these two groups. Everything you need to know about A/B testing to solve this problem can be found here: https://towardsdatascience.com/simple-and-complet-guide-to-a-b-testing-c34154d0ce5a

[Simple and Complete Guide to A/B Testing
End-to-end A/B testing for your Data Science experiments for non-technical and technical specialists with examples and…towardsdatascience.com](https://towardsdatascience.com/simple-and-complet-guide-to-a-b-testing-c34154d0ce5a "towardsdatascience.com/simple-and-complet-g..")

To solve this problem learn the following basic functions in SQL:

SELECT
COUNT
AVG
LEFT JOIN, RIGHT JOIN
WHERE
GROUP BY
HAVING
ORDER BY
LIMIT

You should be able to calculate metrics such as average screen time per control and experimental group where user information is in one table and screen time is in another. This means you should be able to join two tables and also keep the data only for the users who partipated in the A/B test (LEFT JOIN or RIGHT JOIN) depending on your choice of table ordering.

For example:

One thing you want to keep in mind is that you only need the usage data of the A/B test users after the A/B test started for them.

Part 3: A/B Testing Question

The third and final section of the interview is about A/B testing. These are static questions that you can find in every single experimentation-related interview such as:

p-values
statistical significance
hypothesis-testing
t-test vs z-test
confidence interval
Type I and Type II error
and more

Study the following 2 blog posts that contain everything basic statistical concepts such as p-values etc and about A/B testing, then you will be able to answer all the questions asked during this last part of the tech screen.

[Fundamentals Of Statistics For Data Scientists and Data Analysts
Key statistical concepts for your data science or data analytics journeytowardsdatascience.com](https://towardsdatascience.com/fundamentals-of-statistics-for-data-scientists-and-data-analysts-69d93a05aae7 "towardsdatascience.com/fundamentals-of-stat..")

Image Source: cottonbro

Disclaimer*: you can find more information about the type of questions to expect during Spotify or any other company’s interview questions on the websites such as Glassdoor.com.*

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