Senior Experimentation Scientist

**We power people's progress.**:
At Preply, we're all about creating life-changing learning experiences. We help people discover the magic of the perfect tutor, craft a personalized learning journey, and stay motivated to keep growing. Our approach is human-led, tech-enabled - and it's creating real impact. So far, 90,000 tutors have delivered over 20 million lessons to learners in more than 175 countries. Every Preply lesson sparks change, fuels ambition, and drives progress that matters.

**Meet the team**:
We A/B test most**of our changes on production, both product and technical, before scaling it to all customers. The **Experimentation Squad** owns the whole infrastructure and the framework that are used to make those business-vital decisions.

We define the framework rules, including the overall evaluation criterion, set of target metrics, available test types: student-sided, tutor-sided, clustered; frequentist, bayesian, interleaving; superiority, non-inferiority. We analyze performance of the experimentation program using multiple holdout groups and push product management in the directions, which will improve its results. Finally we're in charge of improving the company's experimentation culture and education, and keeping institutional memory.

Our Data Team is dedicated to empowering top-quality decision-making. Do you want to know how? Visit our Tech Radar to learn about the technologies we use at Preply

**What you'll be doing**:

- Unlock the potential of product and marketing teams by researching and implementing new approaches for hypothesis testing (clustering, interleaving, geolift,..);
- Identifying and designing value-adding insights solutions, leveraging data to optimize our strategy;
- Establish credibility and quality of the experimentation framework;
- Quantify the impact of product and marketing development and distinct initiatives in order to identify growth opportunities and help top management in prioritizing Preply's roadmap;
- Level up the experimentation culture across the company;
- Support engineers to build and maintain high-quality data pipelines;
- Collaborate with product teams to help them tackle technical issues with A/B testing.
- Collaborate with marketing teams to measure the impact of changes in budget relocation.

**What you need to succeed**:

- Extensive experience in the data science & analytics field (5+ years' experience at least);
- Experience in product or marketing experimentation and desire to dive deeper into the sphere and research best industry practices to build state-of-the-art experimentation in Preply;
- Strong curiosity, problem-solving, and problem-finding skills;
- Solid SQL hands-on experience, and strong knowledge of Python (NumPy, Pandas, SciPy);
- Good understanding of statistical analysis concepts such as p-value, null hypothesis, and confidence interval;
- Eagerness to take responsibility for systems that directly impact the company's decision-making process;
- Passion for analyzing data to inform decisions, measuring and monitoring;
- Willingness to educate colleagues (doing knowledge-sharing sessions);
- Excellent written and verbal communication skills. Fluent English is a must.

**Nice to have**:

- Knowledge of Airflow, Redshift (or any other Data Warehouse DBs - Snowflake, BigQuery..)
- Knowledge of Looker, Amplitude, Databricks, or other BI tools;
**Why you'll love it at Preply**:

- An open, collaborative, dynamic and diverse culture;
- A competitive financial package with equity, leave allowance and health insurance;
- Not in Barcelona? We offer an attractive relocation package to join us in our Preply Barcelona Hub
- Access to free mental health support platforms;
- Access to Gympass-partnered wellness and gym centers throughout Spain to promote and support well-being and physical health;
- The opportunity to unlock the potential of learners and tutors through language learning and teaching in 175 countries (and counting).

**Our Principles**:

- **Care to change the world** - We are passionate about our work and care deeply about its impact to be life changing.
- **We do it for learners** - For both Preply and tutors, learners are why we do what we do. Every day we focus on empowering tutors to deliver an exceptional learning experience.
- **Keep perfecting**:

- To create an outstanding customer experience, we focus on simplicity, smoothness, and enjoyment, continually perfecting it as every detail matters.
- **Now is the time** - In a fast-paced world, it matters how quickly we act. Now is the time to make great things happen.
- **Disciplined execution** - What makes us disciplined is the excellence in our execution. We set clear goals, focus on what matters, and utilize our resources efficiently.
- **Dive deep** - We leverage business acumen and curiosity to investigate disparities between numbers and stories, unlocking meaningful insights to guide our decisions.
- **Growth mindset** - We proactively seek growth opportuniti