Evaluating the Quality of a Physics Problem-Solving Ability Instrument on Sound Wave Material Using the Rasch Measurement Model

Abstract

This study aims to analyze the psychometric characteristics of a physics problem-solving ability test instrument on sound wave material using the Rasch model. A descriptive quantitative method was employed, and data were analyzed using Minifacet software. The instrument consisted of eight essay items developed based on Polya’s four stages of problem solving: understanding the problem, devising a plan, carrying out the plan, and looking back. The instrument was administered to 74 Grade XI students from a public senior high school in Cimahi City selected through purposive sampling. Data analysis focused on five aspects: construct validity (unidimensionality), item fit, reliability, item difficulty, and discriminating power. The results showed that the variance explained by Rasch measures reached 57.91%, indicating good unidimensionality. All items met the Rasch model fit criteria and were empirically valid. The instrument achieved an item reliability coefficient of 0.98, categorized as excellent. Item difficulty analysis classified three items as easy (1a, 1c, and 2a), three as moderate (1b, 1d, and 2c), and two as difficult (2b and 2d), demonstrating a balanced distribution of difficulty levels across Polya’s problem-solving stages. In addition, all items exhibited very good discriminating power, with Point Measure Correlation values ranging from 0.57 to 0.80. These findings indicate that the instrument is suitable for objectively measuring students’ physics problem-solving ability on sound wave material. Further development is recommended by expanding the number of items and involving a larger sample to improve generalizability.