Guides

What the scores mean, where the measures disagree, and what the research actually supports. Every article cites its sources and says where the evidence stops.

Arrived with a four-letter code? The sixteen type pages take each one as a claim about behaviour and say what would show it.

The instruments

What a given test is asking, how it is scored, and what it can establish — before you answer anything. Including the ones whose limits are usually left out.

Comparisons

Two things people are usually asked to choose between, set against each other — including the cases where the honest answer is that they measure different things.

Explainers

One concept at a time: what a score means, what it predicts, and where the limits of the measurement are.