  This resource letter provides a guide to research-based assessment
instruments (RBAIs) of physics and astronomy content. These are standardized
assessments that were rigorously developed and revised using student ideas and
interviews, expert input, and statistical analyses. RBAIs have had a major
impact on physics and astronomy education reform by providing a universal and
convincing measure of student understanding that instructors can use to assess
and improve the effectiveness of their teaching. In this resource letter, we
present an overview of all content RBAIs in physics and astronomy by topic,
research validation, instructional level, format, and themes, to help faculty
find the best assessment for their course.
