Example: alternative text and data for a chart

The same three bars can support different discussions. A monthly report might emphasise steady growth; a resource discussion might need comparison with hours worked. The alternative should suit the chart’s actual purpose in its context.

Here the purpose is limited: show change from January to March and provide each monthly value. The short description explains the change; the table supplies detail. Together they let readers understand the message and make their own comparison.

Blue does not need describing when it is merely a design choice. If colours distinguish series, their meaning matters: identify what the series represent rather than only naming their colours.

Sources: [1]

“Chart of cases” identifies the subject but omits the important pattern. That may be insufficient when the chart exists to show growth. “Cases rose sharply because of the new method” offers more information, but its judgement and causal claim exceed what this table establishes.

“Cases handled increased from 12 in January to 18 in March” is directly checkable. If February matters, add its value of 15 and the increase of three cases per month. If the table follows the chart, every value need not be compressed into one short alternative.

Read the draft without looking at the chart. Are the period and quantity understandable? Then compare each claim with the data. This editorial exercise catches both empty descriptions and confident unsupported interpretations.

The increase from January to March is 6 cases. Relative to January, that is 6 divided by 12, or 50 percent. This follows from the table. It says nothing about the reason for the increase.

Do not claim that a new working method increased productivity by 50 percent. The chart shows neither effort, cause nor case complexity.

• Do start and end values match the source data?
• Are the period and unit clear?
• Can readers find the table without seeing the page?
• Does the description convey the chart’s message without inventing a cause?
• Do other patterns also need explanation?

Multiple series, uncertainty intervals or important outliers may need more text. Put that explanation in the document’s normal reading flow and connect it clearly to the chart. A very long alternative text is not always the best place for a complete analysis.

A longer explanation should be navigable as ordinary text. Start with the main pattern, explain relevant exceptions and identify where detail is available. For uncertainty intervals, explain what the interval represents using the underlying evidence rather than guessing from appearance.

Avoid unnecessary repetition. Where the same explanation is visible prose, the image alternative can be shorter and clearly connected to it. Test the sequence of heading, image, description and table so readers neither miss information nor encounter the same long analysis repeatedly.