Standards Based Grading measures how students are performing on learning targets.
The purpose of Standards Based Grading is to determine what a student knows, or is able to do, on specific learning targets, as opposed to simply averaging scores over the semester.
Why are we doing Standards Based Grading?
Put simply, Standards Based Grading aims to clear up the uncertainty about what grades mean.
The goal is to do all we can to make sure that a grade is the best representation of what a student actually knows in the content, and not a measure of anything else.