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Trelleborg Group Interview Questions

A/B Testing

Algorithms

Analytics

Machine Learning

Probability

Product Metrics

Python

Statistics

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Suppose there exists a new airline named Jetco that flies domestically across North America. Jetco recently had a study commissioned that tested the boarding time of every airline, and it came out that Jetco had the fastest average boarding times of any airline.

What factors could have biased this result, and what would you look into?

What could potentially bias the average boarding time in favor of an airline that only flies domestically?

What could potentially bias the average boarding time in favor of an airline that only flies domestically?

Boarding Times Bias

A new airline came out as the fastest average boarding times compared to other airlines.  What factors could have biased this result and what would you look into?

You are testing hundreds of hypotheses with many t-tests. What considerations should be made?

What is a key disadvantage of the F-test when compared to multiple t-tests?

What is a key disadvantage of the F-test when compared to multiple t-tests?

Hundreds of Hypotheses

You are testing hundreds of hypotheses with many t-tests. What considerations should be made?

The schema below is for a retail online shopping company consisting of two tables, <code>attribution</code> and <code>user_sessions</code>.

<ul>
<li>The attribution table logs a session visit for each row.</li>

<li>If <code>conversion</code> is <code>true</code>, then the user converted to buying on that session.</li>

<li>The <code>channel</code> column represents which advertising platform the user was attributed to for that specific session.</li>

<li>Lastly the <code>user_sessions</code> table maps many to one session visits back to one user.</li>
</ul>

First touch attribution is defined as the channel with which the converted user was associated when they first discovered the website.

Calculate the first touch attribution for each <code>user_id</code> that converted. 

Example:

Input:

<code>attribution</code> table

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>session_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>channel</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>conversion</code></td>
<td>BOOLEAN</td>
</tr>
</tbody>
</table>
<code>user_sessions</code> table

<table>
<thead>
<tr>
<th>column</th>
<th>type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>session_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
Example output:

<table>
<thead>
<tr>
<th><code>user_id</code></th>
<th><code>channel</code></th>
</tr>
</thead>

<tbody>
<tr>
<td>123</td>
<td>facebook</td>
</tr>

<tr>
<td>145</td>
<td>google</td>
</tr>

<tr>
<td>153</td>
<td>facebook</td>
</tr>

<tr>
<td>172</td>
<td>organic</td>
</tr>

<tr>
<td>173</td>
<td>email</td>
</tr>
</tbody>
</table>

First Touch Attribution

Are you a talent looking to build business skills, gain experience, and take on exciting challenges? Grow your career with Trelleborg and start shaping the industry from the inside. Summary of the roleAs a Software Engineer - Web Java Development, you will be responsible for the development of secure, scalable, and high-performance applications across our web ecosystem. You will own the end-to-end lifecycle from design and development through deployment and maintenance for critical segments of our websites. This role demands deep expertise in Java, building robust RESTful APIs, and modern frontend development using React. Strong experience with relational databases (RDBMS) is essential. About the Job<ul><li>Development & Design: Design, develop, test, and maintain software applications & services keeping my mind the security aspect in design and development.</li><li>Back-End Development: Design, build, and maintain efficient, reusable, and reliable Java code. Implement RESTful APIs using the Jersey framework to ensure seamless data exchange.</li><li>Front-End Development: Develop responsive, user-friendly, and performant user interfaces and components using React and its ecosystem (e.g., Node, Redux, Hooks etc).</li><li>Database Management: Design and optimize database schemas and write complex, efficient queries, stored procedures, and functions for both Microsoft SQL Server and PostgreSQL.</li><li>Code Quality: Ensure the best possible performance, quality, and responsiveness of applications. Ensure code is well- documented and adheres to industry best practices.</li><li>Collaboration: Work closely with cross-functional teams, Devops team, Designers, Integration and Business touch points to understand requirements and translate them into technical solutions.</li><li>DevOps: Participate in deployment, monitoring, and maintenance activities within a Continuous Integration/Continuous Deployment (CI/CD) pipeline.</li><li>Troubleshooting: Diagnose and resolve complex production issues efficiently</li></ul> About the Ideal CandidateEducation & Experience:<ul><li>Bachelor’s degree in computer science or related field.</li><li>At least 3-4 years of Experience in development of complex Java web projects</li><li>Knowledge in ReactJS or JavaScript library</li><li>Knowledge in developing and implementing complex web solutions</li><li>Excellent know-how of website Architecture (Internet, Intranet and Extranet)</li><li>Experience in the administration of web and application servers</li><li>Good knowledge of Java programming language</li><li>High quality awareness, personal commitment, good social skills, and ability to empathize</li></ul>Competencies:<ul><li>Strong analytical and problem-solving skills.</li><li>Effective time management and tasks prioritization in a dynamic environment.</li><li>Ability to work independently and strong communication skills</li><li>Fluent in English (spoken and written).</li><li> </li></ul>Our Benefits for You<ul><li>Work in the multicultural work environment</li><li>Detailed induction training for your new tasks: You will get to know our company, your contacts, and our structures</li><li>An exciting, multifaceted, and interdisciplinary field of activity.</li></ul>Start shaping the industry from the inside! #ShapingIndustryfromtheInside# Trelleborg is an Equal Opportunity Employer, and we take pride in the diversity of our employees, valuing the special experience and expertise that people from different backgrounds bring to our business. The ability to develop ground-breaking technologies is one of our key assets and our people make it happen.Feel free to contact our HR Team for any questions: Ashwini @ ashwini.venkatesh@trelleborg.com

Question	Topic	Difficulty	Ask Chance
Boarding Times Bias	Statistics	Medium	Very High
Hundreds of Hypotheses	Statistics	Medium	Very High
First Touch Attribution	SQL	Hard	Very High

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