  End-of-course assessments play important roles in the ongoing attempt to
improve instruction in physics courses. Comparison of students' performance on
assessments before and after instruction gives a measure of student learning.
In addition, analysis of students' answers to assessment items provides insight
into students' difficulties with specific concepts and practices. While
open-ended assessments scored with detailed rubrics provide useful information
about student reasoning to researchers, end users need to score students'
responses so that they may obtain meaningful feedback on their instruction. One
solution that satisfies end users and researchers is a grading rubric that
separates scoring student work and uncovering student difficulties. We have
constructed a separable rubric for the Colorado Classical Mechanics/Math
Methods Instrument that has been used by untrained graders to score the
assessment reliably, and by researchers to unpack common student difficulties.
Here we present rubric development, measures of inter-rater reliability, and
some uncovered student difficulties.
