Abstract
This article describes the item parameters analysis result of the space-relations subtest measurement. This subtest is part of the differential aptitude test (DAT) instrument. The item parameters are characteristic psychometric refer quality of the item. The Item parameters than analyzed in this instrument are item fit model, item difficulty, item discrimination, pseudo-guessing, item information curves, and test information function. The data was collected through documentation technique from the space-relation test conducted at Biro Psikologi (Psychology Bureau) UNY, amounting to 1046 students from Yogyakarta, Indonesia. Data were analyzed using item response analysis with the assistance of BILOG program.