Who Is Your Chart For?

This is the fourth in a series of articles that illustrate how basic design principles can improve information display. The previous article focused on cleaning up the details of chart design. Here, we’ll talk about how to define the audience for your chart.

People often come to me wanting to know which visualization is the best one for their situation. Before you pick a chart type or visualization approach, it’s important to understand the context in which the chart will be used. The context for a visualization can be defined in many ways, but ultimately it comes down to understanding both the audience and the purpose for the chart.

Defining your audience

A visualization can speak to many audiences and groups, and each one will have a unique set of needs. I like to include both the person and the high-level task/context in my audience description to help narrow things down. Notice how different the audience needs could be for the first two bullets, even though both focus on experts.

Experts reading a scientific publication to understand someone else’s work
Experts analyzing their data to find something new
Students learning a new concept or idea
Decision-makers (e.g. in a business, people shopping, etc.)
Patients in a hospital
People on the street
Museum-goers interested in seeing something memorable
People on the internet who really love charts (that’s you!)
People who don’t understand or are afraid of math

How broad is your audience?

A figure in a typical scientific journal article will be read by tens or perhaps hundreds of people, most of whom are experts in the field and have made hundreds of similar charts in the past. A poster in the subway will be seen by people from all walks of life, some of whom may not even know how to read a chart, and might be afraid to try. A visualization for an art gallery has quite a broad audience, but the viewers are at least united by the fact that they are all people who go to art galleries, which implies some level of cultural interest and leisure time. You generally want to define your audience as narrowly as possible, but you should also make sure that you are not over-restricting and ignoring common needs.

Think about inclusivity

Good design should be inclusive and accessible. If you find that your choices are excluding a large portion of your audience, you might want to re-think your approach. Usually, making a design more accessible benefits everybody, not just the subset of people who depend on the information that you provide. For instance, adding information and annotations that support understanding and increase interest for one segment of your audience will usually help others as well. Accessibility can be thought of in several different ways:

Legibility/display factors — people must be able to read your visualization in order to benefit from it. This includes people with disabilities, who may have very specific needs.

Text contrast is high enough that you can see the words clearly.
Text is large enough to be read at a glance, or by people with impaired vision.
Colors can be seen by color-blind people.
Colors can be photocopied or printed in black and white.
Screens can be read outside in the sun, or while driving while it’s dark.
Display height (for a poster or piece of art) is such that it is comfortable to read.
Alt-text is available to support screen readers.
Interactions do not rely on fine motor control and the use of a mouse.

Literacy/Graphicacy — people need to understand your visualization to gain value from it.

Use familiar or standard chart types, or include straightforward explanations and tutorials for less common or unfamiliar charts. There’s nothing wrong with a novel graphic, but it’s your responsibility to help people learn how it works.
Clear labels, legends and annotations support understanding.
Step-by-step, logical progression builds understanding and introduces the chart.

Interest — people need to care about your visualization to be impacted or influenced by it.

Visual and aesthetic appeal attract viewers.
Good content and an explicit message give readers a clear takeaway.
It helps if users can see themselves represented in the data, or if there are connections to familiar or relevant contexts.
Tone, use of evidence, choice of language/jargon, and selection of interesting topics support the user in engaging with the piece.

Defining the context for your piece

Black and white image of an empty room with white walls — The context for your visualization should shape your choices. Image source.

Where will your visualization be shown?

Once you understand your audience, it’s important to consider when they will use the visualization, and what their needs are at that time. You need to match the chart type to a user’s actual needs, and those needs may depend on what else is going on.

The best choice of chart often depends on how it will be used:

At a scientific conference
In a museum gallery
On a dashboard or instrument control panel
As a supporting figure in a news article
As the centerpiece of an article from the graphics desk at the NYTimes
In an information dashboard
As the centerpiece of a weekly or monthly report
As the key feature in a website or data product

You might also consider how the viewing context is likely to affect a person’s mental state. Thinking about the expert at a scientific conference, consider how many different things they could be feeling (and possibly all at the same time).

Exhausted after a long day of talks
Excited by new ideas
Overwhelmed by the noise and bustle in a busy conference hall
Worried that this concept might invalidate their own theories
Eager to debate the fine points of their ideas with someone who will actually understand and be interested in their work
Looking for insights that will crack open new ideas and areas to explore

Understanding even a few of these factors can help you think more deeply about what that person needs.

Understand your user

All of these considerations are helping to build a user persona for your audience: a sketch that helps you to imagine your user more clearly, so that you can tailor your design to work for them. This specificity can also eliminate people though, so be careful to choose a persona that is truly representative of your audience. Done poorly, persona can devolve into simplistic stereotypes. Thinking through a range of identities for that core persona can help you to examine your own assumptions about your audience, and gives you a much deeper appreciation for how needs might vary from one person to the next. How does your picture change if the person is: male/female? Black /white /brown? European /American /Asian /African / Middle Eastern? Able-bodied /disabled? Young /old? Educated /uneducated? Rich /poor? A well-known leader /a newcomer in the community?

Consider the user experience

Once we have a sense of our persona, we can start to think about the experience that we want to create. I like to think about user experience in terms of coffee shops.

A coffee shop is a great way to think about user experience. Image source.

If I’m going out for coffee with a friend from out of town, I probably want a coffee shop with nice ambiance and a little flair. Because this is a rare social event and we have lots of time, I’m in this for the experience all the way. I’m likely to be deep in conversation with a friend I don’t get to see very often, so I’m not likely to notice if things take a bit more time, but I am likely to care whether the event feels like a special treat. A little bit of ceremony and some thoughtful touches will really help here. We’re probably going to enjoy looking through the menu and commenting on the different choices, folding that into our dialogue as the conversation warms up. We’ll look around at the decorations, notice whether the chairs are comfortable, and we might even take photos of the foam art on top of our lattes. In this case, the experience is what matters, and I’m actively looking for an environment that helps me to slow down, enjoy the moment, and soak it all in. (Note all of the social and economic assumptions built into this description of an “average” person: it assumes that I have leisure time to meet up with a friend but maybe only a few hours to spend, that we can afford and would feel comfortable in a fancy coffee shop, that we’d prefer to meet in a public place rather than my home, that I might take pictures of my coffee cup — stereotypically, to share on social media — and that I live or can get to a place where such a shop exists.)

Compare this experience with that of a different person coming into the same coffee shop. They’re on their way to present at an important meeting. They didn’t get any sleep the night before because they were so stressed out over their slide deck. The train was late and they’re rushing to get to the office, but they really need a cup of coffee to carry them through the first part of the day. This person is likely to experience the exact same coffee shop completely differently. They’ll be annoyed that there are so many choices, tapping their foot while the barista chats with the person in front of them in line. They probably don’t want foam art, chit chat, or fanciness of any kind: they just need to get their coffee and get out.

Both of these situations are completely reasonable, but they lead to vastly different decisions in terms of how you approach designing a coffee shop. At the end of the day, both people just want a cup of coffee, but how you get there is completely different depending on which set of needs you choose to support: in one case, you go for the long, slow, over-the-top experience; in the other, you want a shipshape production line.

Visualization is very similar: at the end of the day, people just need to access the data, but how they choose to do so will vary greatly depending on the context and their specific task.

If you’re planning to spend an entire Saturday going to a museum or an art gallery, you’re probably going to take the time to explore, and you’ll be delighted to watch a complicated story unfold as you work your way deeper and deeper into an interesting visual narrative. The desire for a memorable experience is what brought you here, and you’re hoping to find something captivating that will draw you in. Emotional and aesthetic gratification will be critical for helping you to stay engaged and interested in that piece, especially when there are so many other interesting things to see.

Image of a visualization designed by Georgia Lupi. — A beautiful example of visualization for a museum, by Giorgia Lupi. Image source.

At the other extreme, imagine that you are a stock broker or a fighter jet pilot whose survival (or career) depends on making split-second decisions under lots of pressure. You don’t have time to carefully peel back the layers of information to expose a deeper story; you need the important information laid out in front of you, all at once. The cleaner and clearer, the better: mistakes can be fatal. Whether this is the best environment for decision-making is a whole different article, but there’s no question that this situation presents a very different set of user needs.

Image of the instrument control panel in a fighter jet. — The cockpit of a fighter jet is a completely different context, with completely different needs. Image source.

For both the coffee shop and the visualization, a single person could match both persona, on different days and at different times. Depending on a user’s experience in that moment, they might have entirely different needs. Forgetting to consider the experience and needs of your user — and how they are situated in that context, and that moment — is a recipe for failure.

Understanding the context of a visualization also helps to create some important boundaries for the form of the visualization, all of which affect our choices for how to design.

Will the visualization be printed or digital, static or interactive?
How long are users likely to spend on the piece?
Will people be looking at this in person, on their phone, on a laptop computer or movie screen?
Will the visualization be viewed close up or from far away?
How many people will be viewing it at one time?

Designing for your audience

All of these considerations can affect chart selection and design in many different ways. Understanding your audience needs or wants can help you begin to frame the different choices for your chart display.

Chart literacy, or graphicacy. Does your user know how to read a chart? Are they fascinated by data, or permanently scarred from a bad math class experience in middle school? How “advanced” a chart are they likely to understand?
Need for quantitative accuracy. How critical is it that your audience is able to read exact numbers from this chart? Are they likely to know how to do so, or do you need to help them out?
Amount of detail required, or desired. Is your audience interested in digging through all of the information and details, or are they mostly interested in getting to the bottom line?
Annotations and supporting information. Do you need to include annotations to explain what’s going on? Would it be helpful to explicitly point out specific facts?
“The reveal.” Is your data best presented as a logical argument, a slow unfolding of information with increasing complexity, or a clear statement of a simple fact?
Display specifics. How much detail will your audience be able to see and interact with? Based on the display context that you’re considering, will users be able to see what they need in your chart?
Tone or approach of your piece. How will you engage your audience? What tone or language is appropriate, and what’s likely to be interesting to them?

Taking all of these different factors into consideration is the first step toward choosing a chart that is appropriate to your context, and that best meets your user’s needs.

Stay tuned for the next installment in this series, where we will get deeper into understanding how your own purpose affects chart choices as well.

Erica Gunn

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Erica Gunn is a data visualization designer at one of the largest clinical trial data companies in the world. She creates information ecosystems that help clients to understand their data better and to access it in more intuitive and useful ways. She received her MFA in information design from Northeastern University in 2017. In a previous life, Erica was a research scientist and college chemistry professor. You can connect with her on Twitter @EricaGunn.