Which chart should I use? Choose and read charts that tell the truth
By the end, you pick the right chart for each question, read any chart without being fooled, and can explain what's wrong with one that misleads.
You go at your own pace, with your Maestro beside you, 1:1, through the whole course: ask it anything, and it asks you questions too.
16 skills · 4 modules
What you'll be able to do
Each box is a skill. The base is at the bottom, recognizing and explaining, and you work your way up to building something of your own and judging what works and why. Hover over a box to see what it builds on. Click it to see where I teach it and how your Maestro checks it.
- Evaluate
- Analyze
- Apply
- Understand
Evaluate
Choose a chart for a question and justify it
Where I teach it: Shape, parts and relationships · When to use a scatter plot?
Builds on:
- Use sorted bars to compare amounts
- Use a line to show change over time
- Use a histogram to see how values are spread
- Use a part-to-whole chart with few parts
- Use a scatter plot to see the relationship between two measures
Your Maestro asks you to judge when it fits and why and saves it as evidence when you do.
Critique a misleading chart and propose a fix
Where I teach it: Charts that mislead by accident · The final challenge: three questions and a chart to fix
Builds on:
- Read a chart in four moves
- Diagnose a bar chart with a cut axis
- Diagnose a dual-axis chart
- Diagnose shapes whose area exaggerates the data
- Diagnose an average that hides how values are spread
- Choose a chart for a question and justify it
Your Maestro asks you to judge when it fits and why and saves it as evidence when you do.
Analyze
Diagnose a bar chart with a cut axis
Where I teach it: Charts that mislead by accident · Why should a bar chart start at zero?
Builds on:
- Explain where axes start and why the baseline matters
- Use sorted bars to compare amounts
Your Maestro asks you to break a problem down with it and saves it as evidence when you do.
Diagnose a dual-axis chart
Where I teach it: Charts that mislead by accident · Why avoid dual-axis charts?
Builds on:
- Explain how the scale (pesos, percent, logarithmic) changes the reading
- Use a line to show change over time
Your Maestro asks you to break a problem down with it and saves it as evidence when you do.
Diagnose shapes whose area exaggerates the data
Where I teach it: Charts that mislead by accident · Why do bubble charts and pictograms exaggerate?
Builds on:
- Explain what a chart measures: units, period and what each mark is
Your Maestro asks you to break a problem down with it and saves it as evidence when you do.
Diagnose an average that hides how values are spread
Where I teach it: Charts that mislead by accident · What does an average hide? Mean vs. median
Builds on:
- Use a histogram to see how values are spread
Your Maestro asks you to break a problem down with it and saves it as evidence when you do.
Apply
Use sorted bars to compare amounts
Where I teach it: Start with the question · When to use a bar chart? Sort the bars to compare
Builds on:
- Name the question the reader needs answered
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Use a line to show change over time
Where I teach it: Start with the question · When to use a line chart? Showing change over time
Builds on:
- Name the question the reader needs answered
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Use a histogram to see how values are spread
Where I teach it: Shape, parts and relationships · What is a histogram and how do you read it?
Builds on:
- Name the question the reader needs answered
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Use a part-to-whole chart with few parts
Where I teach it: Shape, parts and relationships · When to use a pie chart (and when not to)
Builds on:
- Name the question the reader needs answered
- Use sorted bars to compare amounts
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Use a scatter plot to see the relationship between two measures
Where I teach it: Shape, parts and relationships · When to use a scatter plot?
Builds on:
- Name the question the reader needs answered
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Read a chart in four moves
Where I teach it: Read any chart in four moves · Did it grow more in pesos or in percent? A chart's scale
Builds on:
- Explain what a chart measures: units, period and what each mark is
- Explain where axes start and why the baseline matters
- Explain how the scale (pesos, percent, logarithmic) changes the reading
Your Maestro asks you to use it on a new case and saves it as evidence when you do.
Understand
Name the question the reader needs answered
Where I teach it: Start with the question · Which chart should I use? Start with the question
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Explain what a chart measures: units, period and what each mark is
Where I teach it: Read any chart in four moves · How to read a chart without being fooled
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Explain where axes start and why the baseline matters
Where I teach it: Read any chart in four moves · How to read a chart without being fooled
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
Explain how the scale (pesos, percent, logarithmic) changes the reading
Where I teach it: Read any chart in four moves · Did it grow more in pesos or in percent? A chart's scale
Your Maestro asks you to explain it in your own words and saves it as evidence when you do.
What we'll cover
Start with the question
Shape, parts and relationships
Read any chart in four moves
Charts that mislead by accident
Common questions
- What do I need to know before I start?
- No programming and no statistics. If you've ever looked at a chart in a report or a presentation, you have what you need.
- Is it free? Do I need an account?
- It's free. You can read every page without an account. With a free account you enroll in one tap, fix the charts on each page, answer the questions and ask your Maestro.
- Do I have to install anything?
- No. The charts are edited and drawn right on the page. Some exercises change a word or two in code that's already written, and each one tells you what to change.
- I use Excel or Google Sheets. Is this for me?
- Yes. What you learn is choosing and reading, and that doesn't depend on the program. Where it matters, like checking where an axis starts, the page shows you where that option is in Excel and in Google Sheets.
- Is the data real?
- No. La Espiga, the bakery, and its six branches in Guadalajara are made up for the course. It's synthetic data, built so the misleading cases show up: the same average with very different customers, a small branch growing fast, and months with Three Kings bread and pan de muerto.
What you get
- 4 modules and 13 pages, open whenever you want them.
Open to everyone: read all of it, and your Maestro, an AI, answers one question per page, on up to five pages a day.
With a free account: your Maestro for the whole course, always on the page you're on, and the exercises run with nothing to install.
Words you'll meet
In the lessons, tap one to see what it means, or ask your Maestro about it.
Who's teaching you
Sergio Sánchez
I'm Sergio, chekos online. I've worked with data for about ten years, mostly at mission-driven organizations: policy research first, then education, and now early childhood services. In 2018 I started tacosdedatos to share what I was learning, and since then it's been a blog, a podcast, courses, guides, and a community. These days I spend a lot of my time building with AI agents and writing about how I organize my work around them. I share what I've learned; you take what's useful and make it yours.
See you in the course
Which chart should I use? Choose and read charts that tell the truth