Patterns of Performance Across Different Types of Items Measuring Knowledge of Ohm’s Law

The purpose of this study was to examine patterns of student performance across different types of assessment items to determine if the tasks were indeed measuring the intended knowledge components. Students completed both performance and multiple-choice test items intended to measure their knowledge and understanding of Ohm’s law: voltage, current and resistance. The results of the study indicate that, for less complex concepts, performance on multiple choice items and items requiring written explanations is comparable. For more complex knowledge units, such as the concept of current, performance is less stable across formats. The study also found that performance on multiple choice items asking students to make predictions about the effects of changes in circuits was sensitive to the component of the circuit being manipulated. Thus, in some cases, estimates of student knowledge can be influenced by very minor contextual changes to items that have the same format and were designed to tap similar knowledge and skills. This research adds to a growing body of evidence that inferences about students’ knowledge in a particular domain may depend, to a large extent, on the manner in which students are asked to display their knowledge.