Data Scientist – Experimentation, Personalization

This is a fully remote position, open to applicants in Spain.

📋 Description

• Enhance our recommendation and personalization strategies by creating and validating innovative statistical methods - ranging from advanced segmentation models and engagement scoring to causal uplift estimation and multi-touch attribution.

• Take ownership of the experimentation framework for the team: design rigorous A/B and multivariate tests, develop approaches to address complex measurement challenges (novelty effects, interference, long-term impacts), and ensure accurate interpretation of results.

• Address intricate analytical challenges that necessitate moving beyond descriptive statistics - constructing predictive models, conducting causal inference analyses, and breaking down metric fluctuations into their underlying factors.

• Collaborate closely with the Senior Analyst to transform user journey insights into statistically sound targeting and personalization strategies.

• Work alongside the ML Engineering Data Scientist to guarantee that statistical models and experimental outcomes can be generated and integrated into the recommendation engine.

• Define and enhance the metrics and success criteria used to assess personalization quality, ensuring that we measure what truly matters for users and for the business.

• Manage the offline evaluation framework: develop and maintain counterfactual evaluation methods, replay-based policy estimation, and offline screening pipelines that allow the team to evaluate 10 ideas offline for every 1 tested live - significantly speeding up iteration cycles.

• Analyze and measure the relationship between editorial guidelines and personalization logic - systematically exploring when and how rules like hardcoded IP placements, content diversity constraints, or curated onboarding slots interact with ML-optimized recommendations, and designing experiments to quantify the trade-offs.

• Articulate complex statistical findings clearly and confidently to non-technical stakeholders, while advocating for methodological rigor across the team.

⛳️ Requirements

• Solid statistical foundation: extensive knowledge in probability, statistical inference, regression modeling, and causal inference techniques (A/B testing, difference-in-differences, propensity score matching, uplift modeling).

• Proficient in Python for data science: adept in Python (Pandas, Numpy, Scipy, Statsmodels, Scikit-learn) for analysis, modeling, and prototyping. Produces clean, reproducible, version-controlled code.

• SQL and data pipelines: strong SQL capabilities for large-scale data warehouses (Databricks or similar). Comfortable with DBT or comparable transformation layers to establish robust analytical foundations.

• Expertise in experimentation: has designed and executed A/B tests end to end in a product context, including power analysis, metric selection, and managing complex scenarios (novelty effects, network interference, multi-armed bandits).

• Insight into recommendation and personalization: experience evaluating or enhancing how a system determines which content, products, or actions to present to users. Understands the essential trade-offs in personalization - relevance vs. diversity, exploration vs. exploitation, short-term engagement vs. long-term value - and has worked on assessing whether recommendations genuinely assist users, rather than merely optimizing a metric.

• Strong problem-solving skills: comfortable navigating ambiguous, open-ended challenges and structuring a thorough path to solutions. Avoids defaulting to simple answers when the problem requires more depth.

• Product and business acumen: connects statistical work to business outcomes. Asks the right questions before responding to the presented ones. Has influenced product or personalization strategy with data-driven recommendations.

• Effective collaboration: operates efficiently at the intersection of analytics, product, and engineering. Translates statistical complexities into clear implications without oversimplifying.

• Nice to have: Experience in building offline evaluation frameworks for ranking or recommendation systems (counterfactual evaluation, replay estimation, interleaving).

• Experience with recommendation systems or content personalization from a statistical/modeling perspective (e.g., collaborative filtering, contextual bandits, learning-to-rank).

• Familiarity with Bayesian inference or probabilistic modeling.

• Experience with experimentation platforms such as Amplitude or GrowthBook.

• Background in subscription or freemium product analytics.

• Proficiency in English is essential: We’re a multicultural team providing services in English; while certifications aren’t required, fluency is crucial. As a fully remote company, clear and effective spoken and written communication, particularly in asynchronous and long-form formats, is vital for successful collaboration.

🏝️ Benefits

• Career Growth: Your development is key to our success! We invest in your growth with up to €2,000 per year for books and training, enabling you to continue learning and advancing with us.

• Remote-Friendly: Work from wherever you are most productive, whether at home or in our offices in Madrid, anywhere within a 2-hour difference from Spain (GMT+1).

• Stock Options: Your contributions matter! You'll receive stock options, allowing you the opportunity to own part of the company and share in its success.

• Home Office Setup: Create your ideal workspace with a €400 allowance for setup and €35/month for remote work expenses, as comfort fuels creativity!

• Meal Allowances: Enjoy €60/month on your Cobee card for meals at restaurants or food delivery, because good food enhances everything!

• Flexible Compensation: Easily manage your meal, transport, and childcare costs with Cobee, integrating them directly into your payroll.

• Health Insurance: Access private health coverage at exclusive rates through Adeslas, conveniently deducted from your payroll, ensuring quality care is simple.

• Language Lessons: Learning never stops! Benefit from free language classes in Spanish and English to enhance your skills and stay connected in a global team.

• Visa Sponsorship: If you require a visa to work in the EU, we’ll manage the process and cover the costs to ensure a seamless transition.

• Company events: Yes! We’re a fully remote team spread across various countries, but we love coming together occasionally in different parts of Spain for team gatherings and rejuvenating at our fantastic off-sites!