Soffil Widadah, Tatag Yuli Eko Siswono, Rooselyna Ekawati
This study aims to develop an assessment instrument that is able to measure students' abductive reasoning ability in algebraic proof, as well as to evaluate their abductive reasoning ability. This research is development research with steps: compiling task specifications, writing tasks, reviewing tasks, conducting task trials, analysing task items, improving tasks, and assembling tasks. The instrument trial was conducted on 13 mathematics education students who had taken the number theory course. Research data were collected using algebraic proof tasks designed to assess abductive reasoning in the context of algebraic proof. The results showed that the instrument developed was valid and reliable. The validity of the instrument was tested using Aiken's formula, and the V value obtained for all task items was 1.0, (very good validity). The instrument is also reliable, with a Cronbach's Alpha coefficient value of 0.856, which is (high level of reliability). The results of the pilot test of the instrument showed that students' abductive reasoning ability in algebraic proof was in the medium category, with the majority of students showing a fairly good ability to develop hypotheses and draw conclusions based on available data. In general, the tasks given were able to interpret students' abductive reasoning well, although there were still some areas that needed improvement. This study contributes to the development of a holistic mathematics assessment, measuring not only the result but also the students' reasoning process in mathematical proof. © 2025 Author(s).
Department of Mathematics Education, Surabaya State University, Surabaya, Indonesia
