<![CDATA[This classroom action research was motivated by the low self-efficacy of fifth-grade students in mathematics learning, particularly on whole number material. Students tended to lack confidence in solving mathematical problems, hesitated to express their ideas, and easily gave up when facing challenging tasks. This study aimed to improve students’ self-efficacy through the implementation of Project Based Learning (PjBL) using the Population Data Fair project. The research was conducted at SDN Sukun 1 Kota Malang during the 2025/2026 academic year and involved 28 fifth-grade students. The study employed a Classroom Action Research (CAR) design consisting of two cycles, each including planning, action, observation, and reflection stages. Data were collected through self-efficacy questionnaires, observation sheets, and documentation. The indicators of self-efficacy were adapted from Bandura’s theory, including confidence in completing mathematics tasks, willingness to face challenging problems, persistence in overcoming difficulties, confidence in collaborative work, self-confidence in presentations, and optimism in achieving learning success. The findings revealed that the implementation of the Population Data Fair project effectively improved students’ self-efficacy. The average self-efficacy score increased from 69.49% in Cycle I, categorized as good, to 85.86% in Cycle II, categorized as very good, resulting in an increase of 16.37%. These findings indicate that Project Based Learning through the Population Data Fair project can serve as an effective learning strategy to enhance students’ self-efficacy in learning whole numbers at the elementary school level.]]>
