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data and analytics recruitment is our core business and we’re proud to say, our customers believe we’re good at it. in our most recent customer satisfaction survey, 95% of respondents said that they would recommend harnham. harnham has actively chosen to focus on data and analytics, we’ve immersed ourselves in this market and are now an integral part of this business community. our capability has grown to provide recruitment services and advice across the marketing analytics, credit risk, data science, data and technology and digital sectors.

data and analytics recruitment is our core business and we’re proud to say, our customers believe we’re good at it. in our most recent customer satisfaction survey, 95% of respondents said that they would recommend harnham. harnham has actively chosen to focus on data and analytics, we’ve immersed ourselves in this market and are now an integral part of this business community. our capability has grown to provide recruitment services and advice across the marketing analytics, credit risk, data science, data and technology and digital sectors.

Overview

A/B Testing

Algorithms

Analytics

Machine Learning

Probability

Product Metrics

Python

Statistics

Harnham Interview Guides

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?

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?

Staff Machine Learning Engineer – Robotics Location: Vancouver (Hybrid Onsite)Compensation: $200-250k Base + Equity A leading robotics and AI organization is growing its Machine Learning team and hiring ML Engineers to help build the systems that power the next generation of general purpose robots. This is a rare opportunity to work directly at the intersection of advanced ML and real-world robotics, with access to in-house robotic platforms and a team of experts in perception, manipulation, planning, and control. The OpportunityYou’ll design and implement the software that trains, evaluates, and deploys ML policies on physical robots. This includes building scalable ML pipelines, running high fidelity experiments, integrating novel research into production systems, and shaping the infrastructure that enables robots to learn and operate safely and reliably. What You’ll Work On<ul><li>Build and deploy ML models that run on real robots</li><li>Design training, evaluation, and data collection systems</li><li>Improve model performance, robustness, and scalability</li><li>Test algorithms in simulation and on hardware, resolving issues end to end</li><li>Explore new research ideas and identify high impact opportunities</li><li>Collaborate with researchers, roboticists, and engineers across the organization</li></ul> What You Bring<ul><li>Master’s or PhD in CS, Engineering, Math, or related field</li><li>3+ years hands on ML experience (RL, IL, CV for robotics, or NLP)</li><li>4+ years software engineering experience building production quality systems</li><li>Background in robotics is required</li><li>Experience deploying ML models outside of research settings</li><li>Strong Python and C++ skills</li><li>Proficiency with PyTorch or TensorFlow</li><li>Experience with ROS2, parallel computing (CUDA/OpenMP), and cloud environments is a plus</li></ul>

Senior Data EngineerSalary: £95,000Location: Remote First (London Office)Join a team where data engineering isn't just support, it's the engine. Build the models and pipelines that fuel innovation, accelerate growth, and elevate how the whole company thinks about data.The Opportunity This opportunity puts you at the centre of shaping the company's data landscape, giving you the ability to influence how teams access, understand, and trust their data. You'll take ownership of high-impact initiatives that drive better decision-making and unlock meaningful insights across the business.As a senior contributor, you'll help define the long-term vision for data, ensuring it grows in a scalable, reliable, and forward-thinking direction. You'll mentor and support other engineers, fostering a culture of collaboration, learning, and empowerment. Ultimately, this role offers the chance to make a visible, lasting mark by elevating the organisation's data capabilities and enabling teams to work smarter and more independently.The Role & ResponsibilitiesA Senior Data Engineer is responsible for designing and maintaining high-quality, production-ready data pipelines that serve a variety of internal teams. They build and optimise central data models that support analytics, machine learning, and operational use cases. The role involves working with modern data stack technologies such as Databricks, AWS, dbt, Airflow, and Looker.They lead complex technical initiatives, improve engineering efficiency through better CI/CD, observability, and tooling, and ensure data reliability at scale. Senior Data Engineers also mentor junior engineers and help promote a strong, collaborative, self-service data culture.Interview Process<ol><li>Introductory Conversation - 1 Hour</li><li>Pair Programming -1 Hour</li><li>Code Based Task - 1 Hour</li><li>Culture Fit </li></ol>Join as a Senior Data Engineer to build robust data pipelines, shape high-quality models with modern tech, and lead impactful engineering initiatives that empower data-driven decision-making, apply now.

Staff Research Scientist – Robotics & Machine LearningLocation: Vancouver (Hybrid – at least 2 days onsite)Compensation: $200–300k base + equity A pioneering robotics and AI team is hiring a Staff Research Scientist to push the boundaries of embodied intelligence. In this role, you’ll work end to end across research, simulation, and real-world deployment, developing ML-driven control systems for dexterous humanoid robots. You’ll shape the direction of reinforcement and imitation learning research, design scalable training and data pipelines, run large-scale simulation experiments, and bring cutting-edge algorithms onto robots equipped with advanced sensing capabilities. This is a rare opportunity to contribute research that transitions directly into physical, real-world performance. What You’ll Do<ul><li>Develop and advance RL/IL algorithms for complex manipulation tasks</li><li>Lead high-impact research directions and guide experimentation strategy</li><li>Design training and data-collection systems that speed up deployment</li><li>Improve efficiency, reliability, scalability, and compute performance of learning systems</li><li>Run experiments in simulation and on real robots, debugging end to end</li><li>Diagnose failures and design robust, production-ready solutions</li><li>Collaborate closely with ML researchers, robotics engineers, and applied teams</li></ul> What We’re Looking For<ul><li>PhD in ML, Robotics, Computer Science, Applied Math, or equivalent expertise</li><li>5+ years building and deploying robotic manipulation systems (simulation + real robots)</li><li>5+ years hands-on experience with RL/IL for real-world robotics</li><li>4+ years developing large-scale parallel simulation pipelines</li><li>Strong background in continual learning and sim-to-real transfer</li><li>Experience transitioning ML research into production robotic systems</li><li>Publication record in top-tier robotics/AI venues (ICRA, IROS, CoRL)</li></ul> Technical Strengths<ul><li>Expert Python</li><li>Proficiency with PyTorch or TensorFlow</li><li>Experience with ROS2 and parallel compute (CUDA, OpenMP)</li><li>Deep understanding of RL theory and practical implementation</li></ul>

???? Job Opportunity: Lead AI Engineer | Remote | New AI TeamLocation: Fully RemoteRole Type: Full-TimeSeniority: Lead / SeniorStart Date: ASAP ???? About the CompanyThe company is building a brand-new AI function to power the next generation of intelligent products and automation capabilities. With a focus on generative AI, large language models, and cutting-edge applied research, they are searching for a seasoned Lead AI Engineer to help architect, develop, and scale core AI capabilities across the business.This is an opportunity to join at the ground floor, shape the technical direction of the AI stack, and work with a highly collaborative team committed to innovation. ???? The RoleThe Lead AI Engineer will take ownership of designing, building, and deploying advanced AI systems with a strong focus on generative AI and LLM-based applications. This role combines hands-on technical work with leadership responsibilities, including guiding engineering practices, influencing product strategy, and mentoring team members as the AI team grows. ???? Key Responsibilities<ul><li>Architect, build, and deploy generative AI solutions, including LLM-powered applications and retrieval-augmented systems.</li><li>Lead the technical direction of AI projects, ensuring scalability, performance, and reliability.</li><li>Develop high-quality, production-ready Python code and machine learning pipelines.</li><li>Evaluate, fine-tune, and integrate large language models (open-source and API-based).</li><li>Collaborate with cross-functional teams to define AI use cases and translate them into robust engineering solutions.</li><li>Implement best practices for model lifecycle management, observability, and continuous improvement.</li><li>Mentor junior engineers and contribute to shaping a world-class AI engineering culture.</li><li>Stay up to date with research, tooling, and emerging capabilities in the GenAI ecosystem.</li></ul> ???? Required Experience<ul><li>5+ years of professional experience in AI/ML engineering, with a strong background in Python (senior-level proficiency required).</li><li>Hands-on experience fine-tuning, adapting, and deploying large language models (e.g., Llama, GPT-based models, Mistral, etc.).</li><li>Strong understanding of generative AI architectures, prompt engineering, and vector search/RAG systems.</li><li>Experience building production-grade AI applications and data pipelines.</li><li>Proficiency with modern ML frameworks (PyTorch, TensorFlow, JAX) and model-serving frameworks (FastAPI, Triton, Ray, etc.).</li><li>Solid knowledge of cloud platforms (AWS/GCP/Azure) and containerization (Docker, Kubernetes).</li><li>A proven ability to lead technical projects and mentor other engineers.</li><li>Comfort working in a startup or greenfield environment where autonomy and initiative are key.</li></ul> ???? What the Company Offers<ul><li>Fully remote role with flexible working arrangements.</li><li>High ownership in shaping AI strategy, tooling, and technical foundations.</li><li>Competitive salary + equity/benefits package.</li><li>Opportunity to work with cutting-edge GenAI techniques and contribute to innovative products.</li><li>A collaborative environment that values experimentation and engineering excellence.</li></ul>

Data Science ManagerUp to £120,000London (Remote/Hybrid) Company:Join a global marketplace redefining how pre-owned goods are collected, reused, and redistributed. Founded in the UK, they’ve built a scalable, tech-enabled platform that intercepts millions of unwanted items every year, transforming them from landfill-bound to re-loved by new owners. Responsibilities:<ul><li>Lead and deliver scalable statistical models and analyses that drive business decisions</li><li>Own end-to-end delivery of data science projects, from identifying and integrating data sources to experimentation, model deployment, and pricing strategy optimization</li><li>Define and implement best practices in modelling, automation, and process improvements, ensuring the right tools and approaches are used for each problem.</li><li>Effectively communicate complex insights to both technical and non-technical audiences, including senior executives, with a strong focus on commercial impact.</li><li>Collaborate cross-functionally with product managers, engineers, and other stakeholders to align data science work with broader strategic goals under a “One Team” approach.</li></ul> Requirements:<ul><li>MSc or PhD Degree in Computer Science, Artificial Intelligence, Mathematics, Statistics or related fields.</li><li>Strong coding skills in Python and SQL</li><li>Strong communication skills, with the ability to work effectively in a fast-paced, collaborative environment.</li></ul> **Please note that this role does not offer visa sponsorship**

Data Scientist - Pricing & PromotionsLocation: London (1/2 days in office per week)Salary: Up to £650 a day (Inside IR35)Contract: 3 months initially (strong potential to extend) What you'll be doing:<ul><li>Design and refine pricing models that balance growth, profit and competitiveness.</li><li>Explore price elasticity and run scenario analyses to predict the impact of pricing decisions on demand and profitability.</li><li>Analyse promotional and campaign data, including A/B tests, to assess performance and recommend improvements.</li><li>Partner with commercial, marketing, and finance teams to turn analytical insights into real-world pricing and promotion strategies.</li></ul> Tech & Skills:- Strong SQL (Google SQL in particular).- Python or R for statistical analysis.- Experience with regression, hypothesis testing, and other statistical methods.- Strong communication skills and a commercial focus.This is a fantastic opportunity for a data professional who loves solving complex pricing problems and wants to see their insights drive measurable business outcomes.

Product Analyst - £55,000 (Hybrid - London) Industry: Consumer Marketplace / Mobile App Department: Product & InsightsWe're looking for a Product Analyst to join a fast-growing consumer marketplace used by millions globally. You'll work closely with product managers, designers, and engineers to uncover insights, shape user experiences, and drive commercial performance. What You'll Do <ul><li>Analyse user behaviour and product performance across key journeys</li><li>Build dashboards and self-serve insights for cross-functional teams</li><li>Support A/B testing: design experiments, interpret results, recommend next steps</li><li>Work with data and platform teams to ensure clean, scalable datasets</li><li>Present clear, actionable insights that influence product strategy </li></ul>What We're Looking For <ul><li>Strong SQL skills and experience working with large datasets</li><li>Comfortable using Python for product analytics</li><li>Experience with product experimentation / A-B testing</li><li>Familiarity with Looker, Tableau, or similar BI tools</li><li>Confident communicator who can simplify complex data for stakeholders</li><li>Curious, proactive, and thrives in a fast-paced product environment </li></ul>Why Apply <ul><li>Work on high-impact product features used by millions</li><li>Hybrid working, flexible culture, strong learning budget</li><li>Fast-growing environment with real ownership of analysis and experiments</li></ul> Find out more and apply via the link below.

Senior Data Analyst - Marketing Analytics Location: NYC - Hybrid | Salary: $130,000 - $16,000 We're partnered with an innovative technology company that's redefining how people engage with live and digital experiences. With a strong commitment to data-driven decision-making, their Marketing Analytics function plays a central role in shaping growth strategy, optimising performance across channels, and deepening understanding of the customer journey. They're now seeking a Senior Data Analyst to join this high-impact team - someone who can bridge the gap between marketing strategy, business objectives, and analytical insight to drive measurable results. The Role<ul><li>Partner closely with Growth, Marketing, and Product teams to identify opportunities, measure campaign performance, and guide strategic decision-making.</li><li>Own analytical projects end-to-end, from scoping business questions to delivering actionable insights and recommendations.</li><li>Analyse and optimise customer acquisition, engagement, and retention across multiple marketing channels.</li><li>Develop and maintain core marketing datasets and dashboards using tools such as Looker, dbt, and Hex.</li><li>Evaluate campaign and channel effectiveness through experimentation and advanced statistical techniques.</li><li>Communicate complex analytical findings clearly and persuasively to both technical and non-technical stakeholders.</li><li>Act as a thought partner, using analytics to influence broader marketing and growth strategy.</li></ul> What You'll Bring<ul><li>4+ years' experience in Marketing Analytics, Growth Analytics, or a related data-driven role (ideally within tech, ecommerce, or consumer products).</li><li>Strong SQL skills and proficiency in Python or R for data manipulation and modelling.</li><li>Proven experience analysing marketing funnel performance, attribution, and ROI.</li><li>Hands-on experience with experimentation, A/B testing, or incrementality analysis.</li><li>Strong understanding of digital marketing channels, CRM, and performance metrics.</li><li>Excellent storytelling and presentation skills - able to translate data into strategic insight.</li><li>A proactive, collaborative mindset and a passion for driving business impact through analytics.</li></ul> Desirable: experience in B2B2C environments, working with marketing automation or attribution platforms, and exposure to data infrastructure (dbt, event tracking, marketing APIs). Tech StackAirflow | Fivetran | Python | dbt | Redshift | mParticle | Eppo | Mixpanel | Looker | Hex | GitLab If you're passionate about using data to drive marketing performance and influence strategic growth decisions, this is an opportunity to make a tangible impact within a forward-thinking organisation.Get in touch with the Harnham team today to learn more.#MarketingAnalytics #DataAnalytics #GrowthAnalytics #Harnham #DataJobs #AnalyticsCareers

Pricing Analyst (Contract) - SQL & Python £450-£500 per day (Outside IR35) 3-month contract | 2 days per week onsite (London) About the Role A leading organisation is seeking an experienced Pricing Analyst to support a key pricing optimisation project. You will work closely with commercial, finance and data teams to analyse pricing performance, build models, and provide actionable recommendations that drive revenue and margin improvements. Key Responsibilities <ul><li>Analyse large datasets to evaluate pricing performance, commercial trends and customer behaviours</li><li>Develop and maintain pricing models using Python</li><li>Build and run complex queries in SQL to extract and manipulate data</li><li>Present insights and recommendations to senior stakeholders</li><li>Support the wider pricing strategy and contribute to commercial decision-making</li><li>Collaborate with cross-functional teams in a fast-paced environment </li></ul>Required Skills & Experience <ul><li>Strong experience as a Pricing Analyst, Data Analyst, or similar</li><li>Proficiency in SQL and Python</li><li>Solid analytical and quantitative skills, with experience building pricing models</li><li>Ability to interpret complex datasets and translate findings into clear business insights</li><li>Experience working with commercial or financial data</li><li>Strong stakeholder communication skills </li></ul>Contract Details <ul><li>Day Rate: £450-£500 per day (Outside IR35)</li><li>Duration: 3 months (potential extension)</li><li>Location: London - 2 days per week onsite</li><li>Start Date: ASAP </li></ul>Desired Skills and Experience Led pricing analysis and modelling to support commercial decision-making Built and automated pricing models using Python Extracted, transformed and analysed large datasets using SQL Delivered insights on pricing performance, revenue impact and optimisation opportunities Partnered with commercial and finance teams to refine pricing strategy Worked onsite in London 2 days per week as part of a hybrid model Successfully delivered key project milestones within a 3-month engagement

SENIOR DATA ENGINEERUP TO £55,000 + BENEFITSHYBRID - LancashireIf you're a technically strong, proactive Data Engineer looking to join a scaling fintech with start-up energy and enterprise backing, this could be a great next step.THE COMPANY:I'm working on a fantastic opportunity with a high-growth fintech that's transforming how consumers engage with retail and finance. With a modern data stack and ambitious product roadmap, this company is building the future of payments, loyalty, and credit in an agile, tech-driven environment.THE ROLE:You'll join a cross-functional data team as a Data Engineer, working closely with analytics, product, and platform teams to scale and optimise core data infrastructure. This is a hands-on role where you'll take ownership of ingestion, transformation, and modelling-while also helping define platform standards and best practices.Key responsibilities include:<ul><li>Build and maintain ELT pipelines</li><li>Take full ownership of data ingestion</li><li>Support data modelling and architecture within Snowflake</li><li>Own and evolve the dbt layer, including governance and access controls</li><li> Collaborate across analytics, product, and engineering teams</li><li> Contribute to platform improvements, automation, and optimisation</li></ul>YOUR SKILLS AND EXPERIENCE:A successful Senior Data Engineer will bring:<ul><li>Strong SQL skills</li><li>Experience with dbt in a production environment</li><li>Snowflake experience is desirable</li><li>Exposure to AWS</li><li>Confident mentoring peers and contributing to a collaborative, high-impact team</li><li>Experience working in fast-paced, agile environments with modern data workflows</li></ul>THE BENEFITS:You will receive a salary of up to £55,000 depending on experience, along with a comprehensive benefits package. HOW TO APPLY:Please register your interest by sending your CV to Molly Bird via the apply link on this page.

Question	Topic	Difficulty	Ask Chance
Boarding Times Bias	Statistics	Medium	Very High
Hundreds of Hypotheses	Statistics	Medium	Very High
Decreasing Comments	Product Metrics	Easy	Very High

Harnham Interview Questions

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