A mathematics item on the SAT—the Rolling Circle Problem—was found to be faulty. This paper reports a detailed investigation into its mathematical and psychometric properties. In addition to examining performance of the item with more than 100,000 examinees, two small studies were performed with the aid of a physical model of the problem. It was found that the problem could be considered ambiguous due to the nonspecification of the frame of reference, but that almost no one noticed this lack.

A mathematical item on the SAT --the Rolling Circle Problem --was found to be faulty. This paper reports a detailed investigation into its mathematical and psychometric properties. In addition to examining performance of the item with more than lOO~OOO examinees, two small studies were performed with the aid of a physical model of the problem.It was found that the problem could be considered ambiguous due to the nonspecification of the frame of reference, but that almost no one noticed this lack.1.2.

The Advanced Placement Computer Science (APCS) Practice System is an instructional assessment device meant to give students practice in, and feedback on, elementary programming tasks. The system includes a programming editor, item pool, two feedback facilities, and electronic portfolio tools. Students write Pascal procedures using the editor, test them with systemgenerated data, and, for selected problems, can call for a nonsyntactic analysis that produces a partial-credit score and a diagnostic commentary. Results of solution testing and nonsyntactic analysis are recorded by the portfolio tools. This article describes the system's background, instructional model, feedback facilities, and potential uses.The Advanced Placement Computer Science (APCS) Practice System is intended to let students in APCS and introductory courses exercise elementary programming skills and get immediate feedback on their productions. The prototype system is composed of tasks, organized around the theme of manipulating lists, that require the student to write a Pascal procedure. Below, the APCS System's background, instructional model, feedback facilities, and potential uses are briefly described.

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