The Effect of Presenting Geometry Items with and without Shapes on the Psychometric Properties of the Test and Students' Test

This research aimed to examine the effects of presenting geometry items with and without shapes on the psychometric properties of the test and students' test scores. The study was conducted on 480 eighth grade students. Within the scope of the study, two geometry tests were crafted, one with shapes and the other without shapes. Both tests consisted of 15 multiple-choice items. In the data collection process, a counterbalanced design was followed, and the two tests were administered to the students three weeks apart. Analyses were carried out on 405 students who participated in both applications and whose test forms could be matched. The factor analysis results revealed that the factor loadings of the items and extracted variance were higher for the test with shapes compared to the test without shapes. The Cronbach's alpha coefficient of the test containing shapes was found to be significantly higher than that calculated for the test without shapes. According to item difficulties, the questions with shapes were easier for the students than the shape-free questions. In terms of discrimination indices, a difference in favor of the shape- containing test was observed in almost all items. Ferguson's delta statistic, which is a measure of discrimination for the overall test, was higher in the shape-containing test. Correlation analysis denoted a strong positive relationship between students' scores on the two tests. The paired samples t-test proved that there was a statistically significant difference between students' scores on the tests w ith and without shapes. These results indicate that the geometry tests with and without shapes differ in terms of both psychometric properties and students' test scores.