Desi Setiyadi, Zaenuri, Trimurtini
This study aims to examine the psychometric quality of ethnomathematics-based essay items developed to measure elementary school students' mathematical problem-solving abilities through the FOCUS framework (Framing, Observe, Create, Use, and Self-check). This study is grounded in the urgent need to reorient assessment practices, which have traditionally emphasized final answers, toward approaches that more comprehensively represent students' thinking processes in a reflective and contextual manner. A quantitative approach employing the Rasch measurement model was used to analyze student responses in an objective and standardized way. The participants consisted of 65 fifth-grade students in Banyumas Regency, Indonesia, representing both urban and rural school contexts. Data analysis was conducted using the Ministep application to evaluate item fit, reliability, differential item functioning (DIF), and the distribution of student ability and item difficulty through the Wright Map. The findings indicate that all items meet the Rasch model fit criteria, demonstrating strong construct validity in measuring process-based problem-solving abilities. The developed instrument shows exceptionally high reliability (0.99), indicating strong consistency and stability in distinguishing item difficulty levels. Furthermore, the DIF analysis reveals no significant bias based on gender or school location, suggesting that the instrument is fair and inclusive across diverse student groups. The Wright Map demonstrates alignment between students' abilities and item difficulty levels, indicating that the instrument is well-targeted. Therefore, the instrument not only meets strong psychometric standards but also holds pedagogical relevance in supporting meaningful assessment practices. This study contributes to the development of elementary mathematics assessment that is more contextual, reflective, and oriented toward understanding students' mathematical thinking processes. Copyright (c) 2026 The Authors. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Universitas Negeri Semarang, Semarang City, Indonesia
