Use of the coombs elimination procedure in classroom tests

The effectiveness of the Coombs elimination procedure was evaluated with 29 college students enrolled in a statistics course. Five multiple-choice tests were employed and scored using the Coombs procedure. Specifically, students were instructed to mark incorrect rather than correct options and were informed about the scoring method, which discourages guessing. Four indices of performance were calculated to obtain specific indicants of guessing and partial knowledge. Simulated scores were calculated for each test as if the questions were administered using standard procedures. The results suggest that the Coombs procedure decreased guessing, and this effect increased over the grading period. Decreased guessing may account for modest gains in reliability in comparison to reliability of a standard test; however, the decrease from the first to final exam did not improve reliability.