Evidence tiers are a UI problem

Clinical evidence for a variant comes in tiers. The tiers are well defined, widely agreed on, and the source of more design argument than anything else in the product.

Why it is hard

The tier is a summary of a judgement, and the moment you render it as a badge it starts to look like a fact. A tier two variant is not “less true” than a tier one variant. It is supported by a different kind of study. Those are not points on the same scale, but a coloured chip in a sorted column says they are.

We tried a few things. A numeric column read as a ranking. Icons read as a ranking with extra steps. Sorting by tier by default meant nobody ever saw tier three, which was fine right up until the case where tier three was the answer.

Where it landed

The tier is spelled out in words, in the row, next to a short phrase describing what kind of evidence it rests on. It takes more horizontal space than a chip and it is much harder to misread at a glance, which is the entire point.

Colour still carries the tier, because scanning matters, but colour never carries it alone.

The general version

Any time you compress a judgement into a token, you are making a claim about how comparable those judgements are. Usually that claim is not one you would make out loud.