<![CDATA[This study evaluated the psychometric quality of a critical thinking skills test on the kinetic theory of gases using the Rasch Model. The instrument consisted of 18 essay items representing four indicators: basic clarification, advanced clarification, inference, and strategies and tactics. A pilot test was administered to 20 Grade 11 students who had studied the topic, and the responses were analyzed with Winsteps 5.9.0. Principal Component Analysis of Residuals showed that 78.6% of the raw variance was explained by the Rasch measures, indicating a dominant primary dimension. However, the first residual contrast eigenvalue of 4.0963 suggested possible secondary structure. Ten items met the fit criteria, three items (S2, S3, and S6) were misfitting, and five items (S10–S14) were overfitting. Person reliability ranged from 0.95 , while item reliability ranged from 0.96 and was classified as excellent, demonstrating high measurement consistency. Differential Item Functioning analysis identified no statistically significant gender-based item bias. Item difficulty ranged from ?4.02 logits for S15 to 3.12 logits for S3. The Wright Map revealed broad difficulty coverage but also gaps across the ability continuum. Overall, the instrument demonstrated promising preliminary quality, although several items still require revision and further testing with a larger, more diverse student sample and a more balanced gender composition.]]>
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