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Let’s say we have a table with an <code>id</code> and <code>name</code> fields. The table holds over 100 million rows and we want to sample a random row in the table without throttling the database.

Write a query to randomly sample a row from this table.

Input:

<code>big_table</code> table

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

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

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>

Write a query to randomly sample a row from a big table.

Random SQL Sample

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?

Let’s say you work for a social media company that has just done a launch in a new city. Looking at weekly metrics, you see a slow decrease in the average number of comments per user from January to March in this city.

The company has been consistently growing new users in the city from January to March.

What are some reasons why the average number of comments per user would be decreasing and what metrics would you look into?

What metric could be used to measure if active users are still engaging on the platform despite an overall decrease in the average number of comments per user?

What metric could be used to measure if active users are still engaging on the platform despite an overall decrease in the average number of comments per user?

Decreasing Comments

How would you investigate a decline in the average number of comments per user?

Mbta Salaries by Position

The Data Analytics Engineer applies engineering best practices to public transit software systems and products. This is a new role in Customer Technology and will involve evaluating new and emerging data technologies as well as leveraging existing data systems. We use cloud services, open-source software, and modern tools as much as possible. Knowing what to build and reuse ensures that we optimize our time and efforts so we can focus on delivering the best value to our riders. Duties and Responsibilities: <ul><ul><li>Write production-quality software </li><li>Create appropriate unit and integration tests </li><li>Deliver product features on time </li><li>Structure data for consumption by other MBTA departments </li><li>Design systems and architectures that scale </li><li>Communicate openly with the team about issues and improvements </li><li>Collaborate with other engineers to reason through code together </li><li>Protect the data security and privacy of the MBTA and its riders </li><li>Help team members learn skills and overcome obstacles </li><li>Work and communicate effectively with product, design, and other stakeholders within the MBTA </li></ul></ul> Minimum Requirements and Qualifications: <ul><ul><li>Solid understanding of fundamental programming concepts </li><li>Interest in applying functional programming to solve problems </li><li>At least two years of professional experience writing software </li><li>Willingness to work on front and backend depending on the product need </li></ul></ul> Preferences include: <ul><ul><li>Experience with Elixir (can be learned on-the-job), Python, Ruby, or SQL </li><li>Experience with AWS Glue or Spark </li><li>Experience with Terraform or other Infrastructure-as-Code tools </li><li>Experience with Tableau, PowerBI, or other analytics tools </li><li>Experience with GTFS or real-time information </li></ul></ul> Location: This role can be 100% remote or hybrid. As a contracted role for the MBTA, we are only able to employ people living in the following states - ME, MA, NH, RI, and VT. At this time, we are only able to hire US residents who will reside in the US for the duration of their employment Compensation: Pay rate range is $75 - $98 per hour (W-2), up to 1880 hours per year.

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