<![CDATA[This study aims to analyze the profiles and error patterns in the scientific reasoning of upper secondary school students regarding static fluids. This study employs a quantitative approach using a survey design. The study involved 84 students in Malang as respondents, selected through purposive sampling based on the following criteria: having studied static fluids, being taught by the same physics teacher, being enrolled in an active physics specialization class, and being present for the full duration of the test. The test instrument consisted of 10 open-ended questions covering five indicators of scientific reasoning, namely correlational reasoning, proportional reasoning, probabilistic reasoning, control of variables, and hypothetical-deductive reasoning, with a Cronbach’s alpha reliability coefficient of 0.812. The reliability of the instrument and the inter-rater agreement were evaluated through a two-stage inter-rater test using Cohen’s Kappa and the Intraclass Correlation Coefficient (ICC), which yielded an ICC value of 0.981 (very high category). Data analysis was conducted in two stages: quantitatively to measure the level of scientific reasoning, and qualitatively through content analysis to identify patterns of students’ errors. The research shows that students’ average scientific reasoning ability falls within the moderate category (49.42), with the distribution of cognitive levels dominated by the Late Transition (37%) and Early Transition (35%) stages. Only 12% of students reached the Formal Operational level. Proportional reasoning indicators showed the highest achievement, whilst hypothetical-deductive reasoning was the lowest. The highest conceptual understanding was found in Pascal’s Law, followed by Archimedes’ Principle, and the lowest in hydrostatic pressure. The main error patterns identified were students’ difficulty integrating quantitative data into numerical probabilities and their inability to design systematic experiments and identify control variables. These findings indicate that although students passively understand basic concepts, they still struggle with logical justification and procedural reasoning. Keywords: error patterns, scientific reasoning, static fluid.]]>
