Kevalidan Instrumen Authentic Assessment Untuk Mengukur Kemampuan Berpikir Kritis Peserta Didik Pada Problem Based Learning (PBL) Materi Hukum Newton Tentang Gerak

This study developed an authentic assessment instrument based on Problem-Based Learning (PBL) to measure students' critical thinking skills in Newton's laws of motion. We used Thiagarajan's 4D model (1974) to adapt the Research and Development (R&D) method, which includes the following stages: (1) Define (analysis of needs at SMAN 1 Sukoharjo showed that 62% of teachers did not have adequate critical thinking assessment instruments, (2) Design (development of a rubric based on Ennis' indicators, 1996), (3) Develop (expert validation and empirical testing), and (4) Disseminate (limited implementation). Validation by three experts (2 lecturers and 1 teacher) resulted in an average score of 82.48% (highly valid), with details as follows: construct aspect (83.33%), substance (78.02%), and language (86.10%). A pilot test on 35 students using Rasch model analysis (Ministeps 5.4.1) confirmed that 12 items met validity criteria. The instrument has high reliability (Cronbach’s Alpha 0.81) and exceptional practicality (96.16% score based on teacher assessment). The uniqueness of this research lies in the integration of the PBL approach with an authentic assessment rubric structured according to problem-solving stages, as well as the use of Rasch analysis for empirical validation. These findings provide practical contributions for physics teachers in implementing 21st-century skills-based assessment while filling a gap in the literature on specific instruments for Newton's Law material.