Development and validation of a two-tier test instrument on simple electric circuits

In this article, we report the development and validation of a new two-tier concept inventory, the Basic Electricity Assessment of Students’ Thinking (BEAST), designed to assess common conceptual difficulties (“student ideas,” such as current consumption and sequential reasoning) and the understanding of fundamental electric circuit concepts (e.g., current, voltage, and resistance) among undergraduate students. The final version of the BEAST covers six student ideas, each linked to a distinct physical concept. Each student idea is assessed using three two-tier single-choice items. To refine the items and evaluate their content validity, including the correctness of answers and the intended categorization of student ideas based on response patterns, feedback and ratings from five experts were incorporated. The test was administered to a sample of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>N</a:mi> <a:mo>=</a:mo> <a:mn>176</a:mn> </a:math> students enrolled in introductory physics courses across six different German universities. Quantitative evaluation using classical test theory and structural analyses demonstrated strong evidence supporting the test’s content and construct validity. Confirmatory factor analysis utilizing parsimonious bifactor models showed a good fit of the model to the data.