What are some best practices for writing clear and concise captions for your data charts?

1 Use active voice and simple language

One of the main goals of a caption is to describe the main message or takeaway of your data visualization. To do this, you should use active voice and simple language that your audience can easily understand. Active voice means that the subject of the sentence performs the action, rather than being acted upon. For example, instead of writing "The number of sales was increased by the new marketing campaign", you can write "The new marketing campaign increased the number of sales". This makes your caption more direct and engaging. Simple language means that you avoid jargon, technical terms, or acronyms that your audience may not be familiar with. If you have to use them, make sure you define them or provide context. For example, instead of writing "The ROI of the project was 25%", you can write "The project returned 25 cents for every dollar invested (ROI)".

2 Include relevant details and comparisons

Another goal of a caption is to provide relevant details and comparisons that help your audience interpret your data visualization. Depending on the type and purpose of your data visualization, you may want to include information such as the source, the time period, the units, the scale, the categories, the trends, the outliers, the patterns, or the relationships. For example, if you are showing a line chart of the monthly sales of a product, you may want to include the name of the product, the source of the data, the time span, the unit of measurement, the overall trend, and any significant peaks or dips. You may also want to compare your data to a benchmark, a target, a previous period, or a different group. For example, you can write "The monthly sales of Product A increased by 15% from January to June 2020, according to the company's records. This was higher than the average growth rate of 10% for the industry and exceeded the sales target of $50,000 per month".

3 Align your caption with your data visualization

A third goal of a caption is to align your caption with your data visualization, so that they complement each other and do not contradict or repeat each other. You should make sure that your caption matches the title, the labels, the colors, the symbols, and the layout of your data visualization. For example, if your data visualization has a title that summarizes the main message, you do not need to repeat it in your caption. Instead, you can focus on providing additional details or insights. If your data visualization has labels that identify the variables, the units, or the categories, you do not need to explain them in your caption. Instead, you can focus on highlighting the comparisons or relationships. If your data visualization uses colors, symbols, or other visual cues to emphasize or differentiate the data, you should use the same terms or names in your caption. For example, if your data visualization uses blue and red bars to represent male and female customers, you should use the words "male" and "female" in your caption, rather than "blue" and "red".