The Effect of the APOS Approach Assisted by GeoGebra on State Islamic Junior High School Students' Spatial Skills in Geometric Transformations

Abstract

Spatial ability is a crucial component of geometric thinking that supports students' understanding of geometric transformation topics. This study examined the effect of the GeoGebra-assisted Action-Process-Object-Schema (APOS) approach on ninth-grade students' spatial ability in geometric transformations. This study used a quasi-experimental pretest-posttest control-group design with two intact classes at a state Islamic junior high school in Labuhanbatu. The experimental class (n = 33) received instruction using the GeoGebra-assisted APOS approach, while the control class (n = 33) received conventional instruction. Data were collected using a validated spatial ability essay test covering spatial visualization, mental rotation, and spatial perception. The data were analyzed using the Mann-Whitney U test, N-Gain, and Cohen's d. The results showed a statistically significant difference in posttest spatial ability between the two groups (U = 1056.0, p < 0.001), with a higher mean score in the experimental class (90.73) than in the control class (69.70). The experimental class achieved a high mean N-Gain of 0.874, whereas the control class achieved a moderate mean N-Gain of 0.601. The Cohen's d value of 2.856 indicated a very large standardized effect. These findings indicate that the GeoGebra-assisted APOS approach was associated with greater improvement in students' spatial ability in geometric transformations than the conventional approach, although the quasi-experimental design does not permit complete control of potential confounding factors.