Geometry Literacy Scale (GLS): Measuring of Pre-service Mathematics Teachers’ Self-Perceived Competencies

Abstract

Geometry is a fundamental component of mathematical proficiency, yet pre-service mathematics teachers (PMTs) often struggle to demonstrate the holistic literacy required to teach it effectively. Despite its importance, the literature lacks a measurement instrument to assess perceived geometry literacy among pre-service teachers. This study addresses this gap by defining the concept of “geometry literacy” and developing a valid and reliable Geometry Literacy Scale (GLS) tailored for PMTs. A rigorous scale development process was conducted with a large sample of 865 PMTs, split into two independent groups for Exploratory (EFA) and Confirmatory Factor Analysis (CFA). Analyses yielded a psychometrically sound 32 item instrument with a stable single-factor structure, reflecting the integrated nature of geometric thinking in adult learners. The scale demonstrated excellent internal consistency (Cronbach’s α = .94) and composite reliability (CR = .95). CFA results confirmed that the majority model fit indices indicated acceptable fit. The GLS provides researchers and teacher educators with a valid and reliable instrument for assessing pre-service mathematics teachers’ self-perceived geometry literacy and may support future research, program evaluation, and the improvement of geometry teacher education.