AP 1-5 Scale

Hello,

Does anyone know how the AP grading scale is broken down? Is a 1 in the 0-19.99% range, a 2 in the 0-20-39.99% range, a 3 in the 40-50.99% range, etc etc. Or, is it broken down a different way? Does it vary on a course to course basis or is it universal?