Beyond Data — Investigative Data Journalist

What I do

A number is wrong, and nobody can say why. I take it apart.

I do forensic data analysis. When two systems disagree, a metric moves and no decision explains it, or a definition changed quietly three years ago, I trace the figure back through whatever produced it and establish what the records can actually support.

See the services → Recent projects

Portrait of Sergio Fetter
Sergio Fetter Data journalist · forensic analyst

What I do

The tools and techniques I reach for when I take a question apart. Data wrangling, modelling, and the dashboards and writing that make the findings usable.

  • Python for data science

    Data wrangling, automation and analytics pipelines.

  • Machine learning

    Predictive and classification models with scikit-learn.

  • Deep learning

    Neural networks with TensorFlow and PyTorch for complex patterns.

  • Data visualization

    Interactive charts and visual storytelling in Plotly and Matplotlib.

  • Business intelligence

    Tableau and Power BI dashboards that turn data into decisions.

  • ETL & data engineering

    Reliable pipelines and transformations that hold up in production.

  • SQL & NoSQL databases

    Modelling and querying structured and semi-structured data.

  • Cloud & deployment

    Shipping data apps and models to AWS, DigitalOcean and Render.

  • Dashboard development

    Interactive dashboards in Dash, Streamlit and Flask.

  • Statistical analysis

    Hypothesis testing, regression, and inferential modelling.

  • Data storytelling

    Turning complex findings into clear decisions people act on.

  • Workflow automation

    Automating recurring work with Airflow, Prefect and cron.

Selected casework

A short record of problems traced back to what was actually causing them. Full write-ups on the projects page.

Project 2025

Predicting Car Prices with Multiple Regression

The used car market in the US is massive—we're talking over $300 billion. But here's the thing: predicting car prices isn't as straightforward as you might think. There are tons of variables at play, and understanding which ones actually matter can make or break a pricing model.

  • Python
  • Jupyter
  • Matplotlib
Read the case →

Project 2025

Predicting Academic Success

Every year, millions of students enroll in college, yet approximately 40% don't complete their degrees. With such high attrition rates, universities desperately need better ways to predict student success. But can a single test score really tell us who will thrive in higher education?

  • python
  • matplotlib
  • jupyter
Read the case →

From the writing

Essays, reviews and field notes on how numbers get used — and how they get used wrongly. The full archive is at the blog.

ESSAY Oct 15, 2026

The Long History of Bayesian and Frequentist

The world is filled with rivalries. Different school of thoughts that propel ideas forward. Distinct ideologies that changed the course of a nation or a group of people. Elizabeth I and Mary Queen of Scots. Hamilton and Jefferson. Real …

5 min read

FIELD NOTE Oct 08, 2026

Elements of Data Visualization -- How to Make Yours Stand Out

Data visualization has become part of our daily lives. All you have to do is login to an platform and you are immediately directed to a dashboard with fancy graphs. Our eyes have become so accustumed to seeing these diagrams that unless on…

6 min read

ESSAY Oct 01, 2026

R vs Python the Ultimate Question

Working in this industry for well over a decade, the question, which is better, R or Python, comes up every so often. Python has always been my go-to language, and for many years that’s what I would say. But experience has a way of chang…

2 min read

ESSAY Sep 29, 2026

Why Are AI Leaders Calling for a Slowdown?

For the better part of a decade, the world has watched the dawn of artificial intelligence reshape the technological landscape. Companies such as OpenAI, Anthropic, and Google have been at the forefront of this transformation, developing…

7 min read

ESSAY Sep 18, 2026

What is Prediction Error?

The life of a data scientist can be summed up on predicting errors more so than predicting anything else. No model hits the nail on the head all the time. It is just not possible. It can predict something with a certain level of conf…

3 min read

About

Sergio Fetter

Data journalist · forensic analyst · doctoral researcher

I learned to separate what evidence shows from what it suggests in roles where being confidently wrong carried a cost. I have a master's in journalism and communications, and I am finishing a doctorate in data science on how findings get communicated.

The writing is not a byproduct of the analysis. It is where the analysis becomes real, and it gets the same scrutiny.