Understanding age assurance accuracy

Note: you will probably want to view this post on the web because there is some math notation that uses MathJax to render. window.MathJax = { tex: { inlineMath: [[' , ' ], ['(', ')']] } } I've recently seen a number of pieces of pieces about age assurance that want to talk about the degree to which age assurance mechanisms are "accurate" or "effective". In discussions like this it's common for people to talk about accuracy and effectiveness as if they were unitary quantities that could be measured alo