Which chart should I use? Start with the question
Answer three quick questions about charts and learn the first move of anyone who chooses well: naming the reader's question.
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Before you read anything, three quick questions. They don't count for anything: they're here so that at the end of the course you can see how much your way of reading charts has changed. Answer with the first thing you think.
They all use data from La Espiga, a bakery with six branches in Guadalajara, Mexico. It's made up (synthetic data), but its problems are the ones every office has: someone asks for "a sales chart" and nobody says what it's for.
Check yourself: According to this chart, how many times Chapultepec's sales does Providencia sell?
Check yourself: The average Saturday ticket (what one purchase came to) was 95 pesos at both branches. What can you conclude about their customers?
Check yourself: Your boss asks: "Did our sales go up or down this year?" What do you decide first?
If you hesitated on any of them, you're on the right track: all three have a catch, and in this course you'll take them apart one by one. You'll solve the third one today.
A chart answers a question
The question you hear most in an office is "which chart should I use?" It usually gets answered by looking at the data: I have months, I have branches, I have percentages. But the same data fits in many charts. La Espiga's monthly sales can be drawn as a line, as bars, as a pie or as a table. What decides which one works isn't the data: it's the question in the head of whoever is going to read it.
Think of three people who get the same sales file:
- The director wants to know whether this year was better than last. Her question is about change over time.
- The regional manager wants to know which branch needs support. His question is about comparing.
- The purchasing manager wants to know what share of sales is pan dulce (Mexican sweet bread). Her question is about part of a whole.
Same file, three different charts. Give the twelve-month line to the regional manager and he'll have to guess which branch is doing worst. Give the pie to the director and she won't see any change, because a pie has no time in it.
The five questions
Almost every chart at work answers one of these five questions. Each has a chart that answers it better than the rest, and the rest of the course goes through them one by one.
Compare
"Which is bigger?", "who sold the least?". You compare amounts across categories with no order of their own, like branches or products. Answer it with bars sorted from largest to smallest.
Change over time
"Did it go up or down?", "when did it change?". The bottom axis is time, and what matters is the shape of the path. Answer it with a line.
Distribution
"How much does a customer spend?", "does everyone spend about the same, or is it all over the place?". You want to see how many values of one measure are spread. Answer it with a histogram.
Part of a whole
"What share of the total is it?". The parts add up to one hundred percent. With two or three parts, a pie works; with more, sorted bars with percentages.
Relationship
"When one thing goes up, does the other?". You have two measures of the same days, customers or stores. Answer it with a scatter plot: one dot per case.
These aren't traffic laws. They're where someone with experience starts: first name the question, then choose the chart. When a chart doesn't make sense, the problem often isn't the design or the colors: it answers a different question, one the reader didn't have.
Two cases trip people up at first. The first: the person has two questions ("who sold the most, and how did their year go?"). It's almost always better to make two charts than to force one that does both halfway. The second: nobody tells you the question. Then ask it yourself: "what do you want to decide with this?" That one sentence saves you more redone charts than any design trick.
Have a chart to make this week? Tell your Maestro who it's for and what that person wants to decide.
This is how someone works who does it without thinking. Open each step only once you've tried to guess it.
From the request to the chart
Worked example · 5 steps
La Espiga's regional manager writes to you: "Send me a chart of the branches' sales for Monday's meeting." You have each branch's sales, month by month, for all of 2025. Which chart do you send?
Work out the next step yourself, then open it to compare.
Try it
For each request, write the question the way the person asking would say it, and name which of the five it is. Do it before you read the answers below.
- "Send me how Tonalá's sales are doing since we started opening at night."
- "How much do people spend per ticket? Does everyone spend about the same, or is it all over the place?"
- "Do we sell more horchata on hot days?"
Answers: the first is change over time ("did sales go up after the change in hours?"), the second is distribution ("how are the ticket amounts spread?") and the third is relationship ("when the temperature goes up, do cold drinks go up?"). If you named a different one, that's fine: paste the request and your answer to your Maestro, and ask which word in the request decides it.
One more, this time with the answer marked right away: