Start by counting the whole group
In a fictional comparison, six of 100 icons are shaded for one option and four of 100 for another. The absolute difference is two in 100. The relative reduction is one third. Both descriptions refer to the same picture.
Now imagine the second panel uses only 50 icons, with two shaded. It still represents 4%, but the smaller denominator makes a direct visual comparison harder. Equal denominators let the eye compare like with like.
What a single shaded figure does not mean
An icon is not a named person whose outcome is known in advance. Nor does an array show which individual benefits from a change. It displays an estimated frequency in a defined population over a defined period.
If the underlying study has considerable uncertainty, a crisp grid can look more certain than the evidence. A label such as “estimated outcomes over five years” and an explanation of the plausible range can help preserve that distinction.
Color carries an extra message
Bright red may draw attention to a small affected group. A pale gray background may make the unaffected group nearly disappear. These choices influence what readers notice even when the counts are accurate.
Questions worth asking include: - Are both options shown with the same number of icons? - Does the legend identify the outcome and follow-up period? - Can the graphic be understood without distinguishing red from green? - Are benefits and harms shown on comparable scales?
The CDC Clear Communication Index recommends pairing numeric risk with words or visuals. A visual still needs an explanation. In this example, “six versus four in 100 over the same period” conveys the comparison even if the colors are unavailable or the image is read aloud.
