The effect of instructions on multiple-choice test scores

Most standardized tests instruct subjects to guess under scoring procedures that do not correct for guessing or correct only for expected random guessing. Other scoring rules, such as offering a small reward for omissions or punishing errors by discounting more than expected from random guessing, have been proposed. This study was designed to test the effects of these four instruction/scoring conditions on performance indicators and on score reliability of multiple-choice tests. Some 240 participants were randomly assigned to four conditions differing in how much they discourage guessing. Subjects performed two psychometric computerized tests, which differed only in the instructions provided and the associated scoring procedure. For both tests, our hypotheses predicted (0) an increasing trend in omissions (showing that instructions were effective); (1) decreasing trends in wrong and right responses; (2) an increase in reliability estimates of both number right and scores. Predictions regarding performance indicators were mostly fulfilled, but expected differences in reliability failed to appear. The discussion of results takes into account not only psychometric issues related to guessing, but also the misleading educational implications of recommendations to guess in testing contexts.