Your practice percentage is measuring the wrong thing
Any tool that re-asks the questions you got wrong poisons its own accuracy statistic. Here is how far off it gets, measured.
These are about one question: how do you know when you have practised enough? Every post here argues from the published blueprints or from measurements on our own bank. None of them tells you what an exam costs or how long it runs — Anthropic publishes that, and repeating it badly is how a study site loses the reader it just earned.
Any tool that re-asks the questions you got wrong poisons its own accuracy statistic. Here is how far off it gets, measured.
Scaled scores and weighted blueprints both break the arithmetic people do in their heads.
Being terrible at something worth 2.6% of the exam is cheaper than being mediocre at something worth 33%.
A single number with no interval around it is a guess wearing a lab coat.
Everything above is the reasoning behind one number. The diagnostic produces yours in twenty questions, with the interval that says how much to trust it.