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CCS Global Tech Interview Questions

A/B Testing

Algorithms

Analytics

Machine Learning

Probability

Product Metrics

Python

Statistics

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<p>An online marketplace company has introduced a new feature that allows potential buyers and sellers to conduct audio chats with each other prior to transacting.</p>

<p>Let’s say we have two tables that represent this data.</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>chats</code> table</p>

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

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

<tr>
<td><code>buyer_user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>seller_user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>call_length</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>call_connected</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>marketplace_purchases</code> table</p>

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

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

<tr>
<td><code>buyer_user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>seller_user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>item_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>purchase_amount</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>

<ol>
<li>How would you measure the success of this new feature?</li>
<li>Write a query that can represent if the feature is successful or not.</li>
</ol>


How would you measure the success of an online marketplace introducing an audio chat feature given a dataset of their usage?

Audio Chat Success

<p>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.</p>

<p>What factors could have biased this result, and what would you look into?</p>


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

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?

<p>You are testing hundreds of hypotheses with many <em>t</em>-tests. What considerations should be made?</p>


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

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?

Question	Topic	Difficulty	Ask Chance
Audio Chat Success	Analytics	Medium	Very High
Boarding Times Bias	Statistics	Medium	High
Hundreds of Hypotheses	Statistics	Medium	High