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Praxis Engineering Interview Questions

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Let’s say that your company is running a standard control and variant AB test on a feature to increase conversion rates on the landing page. The PM checks the results and finds a .04 p-value.

How would you assess the validity of the result?

Experiment Validity

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

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?

Praxis Engineering Salaries by Position

Java & NiFi Software Engineer (Mid to Senior Level) We have an immediate need for a Software Engineer with strong Java and NIAGARAFILES / Apache NiFi experience to support Report Authoring and Dissemination (RAD) Tool Suite efforts. Want to join a talented team of engineers who develop, sustain, upgrade, and enhance software and full system solutions using the latest development tools, libraries, and techniques? Then this position is for you! What you will be doing: The Java & NiFi Software Engineer will focus on sustainment and development (to include creating enhancements and additional data flows) of the PULSE tool, which is the primary dissemination platform for SIGINT reporting to the Intelligence Community and partners around the world, with tens of thousands of monthly users. Candidates will be required to work a rotating pager schedule for emergency 24/7 call-in support as required (roughly one week out of every six weeks). Staff may charge 4 additional hours for the week they are on call in addition to hours worked. On average, the PULSE team is paged for after-hours support approximately 1-2 times per month, with most issues resolvable by phone. What you will need: <ul> <li>Bachelor's degree in System Engineering, Computer Science, Information Systems, Engineering Science, Engineering Management, or related discipline from an accredited college or university is required. Four (4) years of additional developer experience may be substituted for a Bachelor's degree. </li><li>Minimum of 3 years of software development experience </li><li>Must have the ability to quickly understand existing code and system architecture </li> <li>Clearance: Active TS/SCI with an appropriate polygraph is required to be considered for this role </li></ul>Required technical skills include: <ul> <li>Java </li><li>NIAGARAFILES / Apache NiFi </li><li>Elasticsearch </li></ul>Additional desired technical skills may include experience with: <ul> <li>Spring Boot </li><li>API development </li><li>Docker </li><li>Agency reporting and dissemination tools </li><li>Agency classification policies </li><li>Familiarity working in an Agile environment, Jira and Confluence </li></ul>Who are we? Praxis Engineering* was founded in 2002 and is headquartered in Annapolis Junction MD - with growing offices in Chantilly VA and Aberdeen MD. Praxis Engineering is a consulting, product, and solutions firm dedicated to the practical application of software and system engineering technologies to solve complex problems. With over 300 employees supporting more than 50 contracts, Praxis brings together world class engineers with proven engineering best practices, domain expertise, commercial technologies and proven agile management approaches to create high value solutions aimed at helping our customers meet their most critical business and mission objectives. *Praxis Engineering is a wholly owned subsidiary of General Dynamics IT. Why Praxis? We are focused on continual learning and evolution. We don't do things because "that's the way we've always done things"; we listen to our employees and adapt to the changing marketplace. We look at the big picture and encourage our engineers to get training and certifications in emerging technologies that will help shape our customer's mission. We've been profitable year after year. We're always on the lookout for great engineers to join the team and we recognize that our employees are the heart and soul of what we do. We focus on recruiting talented people, treating them right, and then allowing them to do what they do best. No red tape. No micromanagement. Smart people want to work with smart people, and we love people who are passionate about what they do, and finding ways to do it better. And then there is the... Benefits <ul> <li>Attractive total compensation package to include competitive salary and medical benefits with an option for FREE employee HSA medical plan! </li> <li>Office perks such as free soft drinks and snacks (both healthy and not-so-healthy) </li><li>Praxis swag (annual gift certificate to purchase top brand Praxis apparel) </li><li>401k contribution/match: combination of profit share/contribution (3.5%) and employer match (up to 4.5%) for a total of 8%. </li><li>Annual bonus plan </li><li>4 weeks Paid Time Off + 10 holidays + comp time eligibility. (30+ days of leave to start!) <ul> <li>We reward longevity! On your 5th work anniversary - you will receive an additional week of PTO to 5 weeks of PTO. Making it 35+ days of leave altogether! </li><li>On your 10th work anniversary - you will receive an additional week of PTO to 6 weeks of PTO. Making it 40+ days of leave altogether! </li><li>At any time, your unused PTO can be traded in for $$$! </li> </ul></li> <li>Carryover a max of 380hours of leave from year to year. You can choose to have a sabbatical one year or trade in your unused PTO for something nice! </li> <li>Student loan repayment Assistance - COMING SOON! </li> <li>Training is a priority! Take advantage of our endless in-house training opportunities - or seek out vendor offered (paid) training opportunities like conferences, certification courses and seminars. <ul> <li>Conferences (recently attended by Praxis employees): AWS Summit, IoT World, Black Hat and DefCon. </li><li>Training & Certifications: Splunk, AWS, Big Data/Cloudera, VMWare, Scrum Master...the list of certifications goes on and on! </li><li>Praxis University: Cyber Research, Data Analytics, IoT, AWS and RedHat course offerings and hands-on training. </li></ul> </li><li>We truly believe the right work-life balance can exist, and it's here at Praxis. Our work is extremely important, but your job is just a part of who you are. When you enjoy your life outside of our walls, you're at your best the next time you walk through our doors. We do all we can to assure that happens every day. </li></ul> Praxis Engineering provides equal employment opportunities (EEO) to all employees and applicants for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability or veteran status, or any other protected class.

Data Scientist As an Expert Data Scientist, you will be part of a mission critical team working with established programmatic and quantitative methods to find patterns and relationships in large data sets; conducting mathematical, statistical or other data-driven problem-solving analysis to identify business operations or intelligence questions by internal and external customers. They are expected to work independently with minimal supervision by first line supervisor or government client. What you will be doing: Independently compile data to address the most complex intelligence issues or problems for senior internal/external customers with minimal supervision, provide accurate, timely, complex and sophisticated data analysis in support of key Agency, US national security, and foreign policy objectives and to shape Intelligence Community (IC) analysis priorities. With minimal supervision, conceive, prepare, and communicate a wide range of strategic, highly complex graphics, computational models/tools, or written/oral assessments to internal and external customers (e.g., policymakers, IC components). Manage projects and associated resources. What you need: <ul><li>8+ years of experience</li><li>Bachelor's degree in quantitative or technical field of study (e.g., statistics, mathematics, computer science, physical science, quantitative social sciences). </li><li>Demonstrated experience generating ideas for revolutionary technologies supporting operations in the hard target mission space.</li><li>Demonstrated experience with entrepreneurial leadership in developing, pitching, selling and deploying new technologies to solve operational problems</li><li>Demonstrated experience in Python development with expertise in Python data analytics packages such as pandas, numpy, scipy, genism, and scikit-learn.</li><li>Demonstrated experience with AI/ML technologies and packages, such as TensorFlow, PyTorch, and scikit-learn.</li><li>Demonstrated experience with ML model development on text data, including NLP, and structured datasets.</li><li>Demonstrated experience with data visualization technologies and packages, such as Kibana, Bokeh, Leaflt/Folium and Tableau.</li><li>Demonstrated experience handling restricted data sets, both at the individual and system level.</li><li>Demonstrated experience working with data spread across multiple enclaves.</li><li>Demonstrated experience documenting and editing the results of technical analysis for publication to non-technical audiences.</li><li>Demonstrated experience solving tough problems by developing repeatable methodologies.</li></ul> Clearance: Active TS/SCI with an appropriate polygraph is required to be considered for this role Who are we? Praxis Engineering* was founded in 2002 and is headquartered in Annapolis Junction MD - with growing offices in Chantilly VA and Aberdeen MD. Praxis Engineering is a consulting, product, and solutions firm dedicated to the practical application of software and system engineering technologies to solve complex problems. With over 300 employees supporting more than 50 contracts, Praxis brings together world class engineers with proven engineering best practices, domain expertise, commercial technologies and proven agile management approaches to create high value solutions aimed at helping our customers meet their most critical business and mission objectives. *Praxis Engineering is a wholly owned subsidiary of General Dynamics IT. Why Praxis? We are focused on continual learning and evolution. We don't do things because "that's the way we've always done things"; we listen to our employees and adapt to the changing marketplace. We look at the big picture and encourage our engineers to get training and certifications in emerging technologies that will help shape our customer's mission. We've been profitable year after year. We're always on the lookout for great engineers to join the team and we recognize that our employees are the heart and soul of what we do. We focus on recruiting talented people, treating them right, and then allowing them to do what they do best. No red tape. No micromanagement. Smart people want to work with smart people, and we love people who are passionate about what they do, and finding ways to do it better. And then there is the... Benefits <ul><li>Attractive total compensation package to include competitive salary and medical benefits with an option for FREE employee HSA medical plan! </li><li>Office perks such as free soft drinks and snacks (both healthy and not-so-healthy)</li><li>Praxis swag (annual gift certificate to purchase top brand Praxis apparel)</li><li>401k contribution/match: combination of profit share/contribution (3.5%) and employer match (up to 4.5%) for a total of 8%.</li><li>Annual bonus plan</li><li>4 weeks Paid Time Off + 10 holidays + comp time eligibility. (30+ days of leave to start!) <ul><li>We reward longevity! On your 5th work anniversary - you will receive an additional week of PTO to 5 weeks of PTO. Making it 35+ days of leave altogether!</li><li>On your 10th work anniversary - you will receive an additional week of PTO to 6 weeks of PTO. Making it 40+ days of leave altogether!</li><li>At any time, your unused PTO can be traded in for $$$! </li></ul></li><li>Carryover a max of 380hours of leave from year to year. You can choose to have a sabbatical one year or trade in your unused PTO for something nice! </li><li>Student loan repayment Assistance - COMING SOON! </li><li>Training is a priority! Take advantage of our endless in-house training opportunities - or seek out vendor offered (paid) training opportunities like conferences, certification courses and seminars. <ul><li>Conferences (recently attended by Praxis employees): AWS Summit, IoT World, Black Hat and DefCon.</li><li>Training & Certifications: Splunk, AWS, Big Data/Cloudera, VMWare, Scrum Master...the list of certifications goes on and on!</li><li>Praxis University: Cyber Research, Data Analytics, IoT, AWS and RedHat course offerings and hands-on training.</li></ul></li><li>We truly believe the right work-life balance can exist, and it's here at Praxis. Our work is extremely important, but your job is just a part of who you are. When you enjoy your life outside of our walls, you're at your best the next time you walk through our doors. We do all we can to assure that happens every day.</li></ul> Praxis Engineering provides equal employment opportunities (EEO) to all employees and applicants for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability or veteran status, or any other protected class.

Software Craftsman/Code Wizard/Digital Alchemist/Software Engineer (We're always looking for great software engineers! And if all of the software engineer positions are starting to look the same, and you may just want someone to review your resume. Go ahead and upload your resume. If you are a fit for a current opening, we will reach out! If you are a fit for a future role, rest assured we will reach out once that role becomes available. Feel free to check back with our Careers site too!!) Whatever you want to call yourself, as our software guru, you'll have the opportunity to apply your expertise to develop software applications that play a critical role in advancing intelligence operations. At the end of the day, you'll know that your work is making a real impact in helping to keep our nation safe and secure. If you're ready to take your Java software engineering skills to the next level in an exciting and rewarding career, we encourage you to apply today. Typical responsibilities: <ul><li>Design, develop, and maintain Java software applications </li><li>Collaborate with other engineers, analysts, and stakeholders to develop requirements and design solutions</li><li>Perform code reviews and ensure code quality and adherence to best practices</li><li>Develop and maintain documentation for software solutions</li><li>Work in a fast-paced, agile environment to deliver software solutions on time and within budget</li><li>Typical Requirements:</li><li>Bachelor's degree in Computer Science or related field</li><li>Strong proficiency in at least one programming language (e.g., Java, C++, Python, JavaScript)</li><li>Strong proficiency in one related frameworks (e.g., Spring, Hibernate)</li><li>Experience with software development methodologies (e.g., Agile, Scrum)</li><li>Experience with database technologies (e.g., SQL, Oracle, MySQL)</li><li>Strong problem-solving skills and ability to work independently and as part of a team</li><li>Ability to obtain and maintain a security clearance</li></ul> Locations: We have locations in the MD, Howard County area, as well as, Northern VA, Fairfax County areas. We also have an office in the Aberdeen, MD area as well. We have some Hybrid opportunities in both MD and VA which will allow a some work from home with a mix of working from site. However, most of our positions will be working from various government sites. Clearance: Active TS/SCI with an appropriate polygraph is usually required to be considered for our software engineer roles. Though, there might be times we can look at engineers with secret clearance on up. Who are we? Praxis Engineering* was founded in 2002 and is headquartered in Annapolis Junction MD - with growing offices in Chantilly VA and Aberdeen MD. Praxis Engineering is a consulting, product, and solutions firm dedicated to the practical application of software and system engineering technologies to solve complex problems. With over 300 employees supporting more than 50 contracts, Praxis brings together world class engineers with proven engineering best practices, domain expertise, commercial technologies and proven agile management approaches to create high value solutions aimed at helping our customers meet their most critical business and mission objectives. *Praxis Engineering is a wholly owned subsidiary of General Dynamics IT. Why Praxis? We are focused on continual learning and evolution. We don't do things because "that's the way we've always done things"; we listen to our employees and adapt to the changing marketplace. We look at the big picture and encourage our engineers to get training and certifications in emerging technologies that will help shape our customer's mission. We've been profitable year after year. We're always on the lookout for great engineers to join the team and we recognize that our employees are the heart and soul of what we do. We focus on recruiting talented people, treating them right, and then allowing them to do what they do best. No red tape. No micromanagement. Smart people want to work with smart people, and we love people who are passionate about what they do, and finding ways to do it better. And then there is the... Benefits <ul><li> Attractive total compensation package to include competitive salary and medical benefits with an option for FREE employee HSA medical plan! </li><li> Office perks such as free soft drinks and snacks (both healthy and not-so-healthy)</li><li> Praxis swag (annual gift certificate to purchase top brand Praxis apparel)</li><li> 401k contribution/match: combination of profit share/contribution (3.5%) and employer match (up to 4.5%) for a total of 8%.</li><li> Annual bonus plan</li><li> 4 weeks Paid Time Off + 10 holidays + comp time eligibility. (30+ days of leave to start!) </li></ul><ul><ul><li>We reward longevity! On your 5th work anniversary - you will receive an additional week of PTO to 5 weeks of PTO. Making it 35+ days of leave altogether!</li><li>On your 10th work anniversary - you will receive an additional week of PTO to 6 weeks of PTO. Making it 40+ days of leave altogether!</li><li>At any time, your unused PTO can be traded in for $$$! </li></ul></ul><ul><li> Carryover a max of 380hours of leave from year to year. You can choose to have a sabbatical one year or trade in your unused PTO for something nice! </li><li> Training is a priority! Take advantage of our endless in-house training opportunities - or seek out vendor offered (paid) training opportunities like conferences, certification courses and seminars. <ul><li> Conferences (recently attended by Praxis employees): AWS Summit, IoT World, Black Hat and DefCon.</li><li> Training & Certifications: Splunk, AWS, Big Data/Cloudera, VMWare, Scrum Master...the list of certifications goes on and on!</li><li> Praxis University: Cyber Research, Data Analytics, IoT, AWS and RedHat course offerings and hands-on training.</li></ul></li><li> We truly believe the right work-life balance can exist, and it's here at Praxis. Our work is extremely important, but your job is just a part of who you are. When you enjoy your life outside of our walls, you're at your best the next time you walk through our doors. We do all we can to assure that happens every day.</li></ul> Praxis Engineering provides equal employment opportunities (EEO) to all employees and applicants for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability or veteran status, or any other protected class.

UI/UX Front-End Software Engineer Praxis Engineering creates exciting and novel mission solutions in the chaotic world of cyber related technologies and products. At the heart of Praxis Engineering are talented and motivated engineering teams empowered to create cutting edge technologies and systems to solve difficult problems for a wide variety of cyber mission operations. We are looking for Software Engineers who are looking to achieve the kind of game-changing leap forward that our customers need across a spectrum of cyber capabilities. What you will be doing: The Software Engineer will serve as the technical lead of multiple software development teams; select the software development process in coordination with the customer and system engineering; recommend new technologies and processes for complex software projects; ensure quality control of all developed and modified software, and delegate programming and testing responsibilities to one or more teams and monitor their performance Responsibilities include: <ul><li> Develops, maintains, and enhances complex and diverse software systems (e.g., processing-intensive analytics, novel algorithm development, manipulation of extremely large data sets, real-time systems, and business management information systems) based upon documented requirements. Works individually or as part of a team</li><li> Reviews and tests software components for adherence to the design requirements and documents test results</li><li> Resolves software problem reports</li><li> Utilizes software development and software design methodologies appropriate to the development environment</li><li> Provides specific input to the software components of system design to include hardware/software trade-offs, software reuse, use of Commercial Off-the-shelf (COTS)/Government Off-the-shelf (GOTS) in place of new development, and requirements analysis and synthesis from system level to individual software components.</li></ul> What you need: <ul><li> Twenty (20) years of experience as a SWE in programs and contracts of similar scope, type, and complexity is required. Bachelor's degree in Computer Science or related discipline from an accredited college or university is required. Four (4) years of additional SWE experience on projects with similar software processes may be substituted for a bachelor's degree.</li><li> Front end development experience</li><li> Flutter, React, Kotlin, Java</li><li> UI prototyping (wireframes, etc)</li><li> Agile experience</li><li> Experience using standard formats - Protobuf, Json, etc</li></ul> Additional desired skills include: <ul><li> Cross-platform UI experience</li><li> Test automation/DevOps</li><li> Complex data analysis/visualization UI experience</li><li> Full stack development experience</li></ul> Clearance: Active TS/SCI with an appropriate polygraph is required to be considered for this role Who are we? Praxis Engineering* was founded in 2002 and is headquartered in Annapolis Junction MD - with growing offices in Chantilly VA and Aberdeen MD. Praxis Engineering is a consulting, product, and solutions firm dedicated to the practical application of software and system engineering technologies to solve complex problems. With over 300 employees supporting more than 50 contracts, Praxis brings together world class engineers with proven engineering best practices, domain expertise, commercial technologies and proven agile management approaches to create high value solutions aimed at helping our customers meet their most critical business and mission objectives. *Praxis Engineering is a wholly owned subsidiary of General Dynamics IT. Why Praxis? We are focused on continual learning and evolution. We don't do things because "that's the way we've always done things"; we listen to our employees and adapt to the changing marketplace. We look at the big picture and encourage our engineers to get training and certifications in emerging technologies that will help shape our customer's mission. We've been profitable year after year. We're always on the lookout for great engineers to join the team and we recognize that our employees are the heart and soul of what we do. We focus on recruiting talented people, treating them right, and then allowing them to do what they do best. No red tape. No micromanagement. Smart people want to work with smart people, and we love people who are passionate about what they do, and finding ways to do it better. And then there is the... Benefits <ul><li>Attractive total compensation package to include competitive salary and medical benefits with an option for FREE employee HSA medical plan! </li><li>Office perks such as free soft drinks and snacks (both healthy and not-so-healthy)</li><li>Praxis swag (annual gift certificate to purchase top brand Praxis apparel)</li><li>401k contribution/match: combination of profit share/contribution (3.5%) and employer match (up to 4.5%) for a total of 8%.</li><li>Annual bonus plan</li><li>4 weeks Paid Time Off + 10 holidays + comp time eligibility. (30+ days of leave to start!) <ul><li>We reward longevity! On your 5th work anniversary - you will receive an additional week of PTO to 5 weeks of PTO. Making it 35+ days of leave altogether!</li><li>On your 10th work anniversary - you will receive an additional week of PTO to 6 weeks of PTO. Making it 40+ days of leave altogether!</li><li>At any time, your unused PTO can be traded in for $$$! </li></ul></li><li>Carryover a max of 380hours of leave from year to year. You can choose to have a sabbatical one year or trade in your unused PTO for something nice! </li><li>Student loan repayment Assistance - COMING SOON! </li><li>Training is a priority! Take advantage of our endless in-house training opportunities - or seek out vendor offered (paid) training opportunities like conferences, certification courses and seminars. <ul><li>Conferences (recently attended by Praxis employees): AWS Summit, IoT World, Black Hat and DefCon.</li><li>Training & Certifications: Splunk, AWS, Big Data/Cloudera, VMWare, Scrum Master...the list of certifications goes on and on!</li><li>Praxis University: Cyber Research, Data Analytics, IoT, AWS and RedHat course offerings and hands-on training.</li></ul></li><li>We truly believe the right work-life balance can exist, and it's here at Praxis. Our work is extremely important, but your job is just a part of who you are. When you enjoy your life outside of our walls, you're at your best the next time you walk through our doors. We do all we can to assure that happens every day.</li></ul> Praxis Engineering provides equal employment opportunities (EEO) to all employees and applicants for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability or veteran status, or any other protected class.

Praxis Engineering Interview Questions

Praxis Engineering Interview Guides

Praxis Engineering Interview Questions

Praxis Engineering Salaries by Position

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