Consistent learning experiences provided to students with intellectual disabilities contribute to the permanence of their learning. Functional academic skills are essential for students to acquire in order to lead independent lives. The skill of pattern formation, which holds a significant place among early mathematical skills, is crucial in minimizing the challenges already faced by students with intellectual disabilities while learning mathematical concepts, given that these students encounter numerous difficulties in learning mathematics (Papic, 2007). "Due to its significance as a skill that needs to be acquired in the preschool special education curriculum, this skill holds importance for students with intellectual disabilities within the group of individuals with special needs. "The aim of this study is to investigate the effectiveness of fixed-time interval instruction in teaching pattern formation skills to students with mild intellectual disabilities. The concept of patterns, which falls within the scope of mathematical skills, is encountered in various aspects of daily life. This study was conducted with three students, aged 6-7, consisting of one male and two females. The research design utilized for this study is the single-subject research model, employing multiple baseline model across participants design.". The independent variable of the study is the presentation of pattern formation skills using the fixed-time interval instruction method, and the dependent variable is the highest level of accuracy achieved in completing target patterns. In the study, data on social validity, reliability, and effectiveness were collected. Linear graphs, a graphical analysis technique, were employed to analyze effectiveness and reliability data, while the analysis of social validity data was conducted qualitatively. As a result of the research, it was observed that the fixed-time interval instruction method was effective in teaching the concept of patterns to preschool children with mild intellectual disabilities, and students demonstrated success in the follow-up data collected in the 1st, 2nd, and 4th weeks. During the generalization sessions, it was also observed that students could generalize their pattern formation skills to different settings using colored covers. Parents and teachers reported that they observed success in participants' efforts related to the pattern concept.

Pattern formation skill, intellectual disability, fixed-time interval instruction