The Pennsylvania Classroom Diagnostic Tools (CDT) is a computer adaptive test (CAT). Similar to other assessments, students complete a CAT by responding to a series of multiple-choice items. A computer adaptive test (CAT) is different because as a student responds to each test question the CAT determines the next test question to ask the student. The CAT uses the student’s responses to determine which follow-up question would give the most information about the student’s performance on the Pennsylvania Assessment Anchors and Eligible Content. This means that each student can be administered a unique set of questions which allows the test to give diagnostic information about each student’s understanding and abilities of the Assessment Anchors and Eligible Content.