Analysis of middle school mathematics textbook units covering the numbers and operations learning domain in terms of number sense

The aim of this study is to examine the inclusion of number sense and its components in the unit contents covering the "Numbers and Operations" learning area in middle school mathematics textbooks for grades 5, 6, 7, and 8. The data sources of the study consist of middle school mathematics textbooks for grades 5, 6, 7, and 8, published by Özgün, Berkay, and Koza Publications, approved by the Ministry of National Education Board of Education, and used in certain regions, including the province where the researcher is employed during the 2023–2024 academic year. The document analysis method was used in the study. The content of the units covering the "Numbers and Operations" learning area was analyzed in terms of topic explanations, activities/examples, and assessment-evaluation questions concerning number sense components. Since the obtained data were summarized and interpreted within predetermined themes, the descriptive analysis technique was employed. Accordingly, the study examined how and to what extent the three number sense components identified in the study by Can and Yetkin Özdemir (2020) "understanding numerical magnitude, using benchmarks, and computational flexibility"—were represented in the textbooks. These components emerged as a result of a factor analysis conducted during the validity and reliability studies of a number sense measurement tool developed by the researchers, consolidating six sub-components proposed by Yang (1995) into three dimensions. As a result of the analysis process, the rates and ways in which number sense components were included in the topic explanations, activities/examples, and assessment-evaluation sections of the units covering the "Numbers and Operations" learning area in the middle school mathematics textbooks for grades 5, 6, 7, and 8 were presented with sample excerpts from the textbooks. When the results of the analysis were evaluated across all grade levels, it was determined that the sixth-grade mathematics textbook contained the highest number of number sense-related content, based on the number of questions, compared to other textbooks. The sixth grade was followed by eighth-grade, fifth-grade, and seventh-grade textbooks, respectively. When the proportion of examples related to number sense in the textbooks was examined, the fifth-grade textbook had the highest proportion, followed by the sixth, seventh, and eighth grades, respectively. When the results were evaluated in terms of the number sense components, the "understanding numerical magnitude" component was most prominently represented, followed by the "computational flexibility" component. No content related to the "using benchmarks" component was identified in the fifth-grade textbook. In the sixth- and seventh-grade textbooks, the "computational flexibility" component was the most frequently represented, followed by the "understanding numerical magnitude" and "using benchmarks" components, respectively. The recommendations derived from the evaluations conducted within the scope of the thesis include the teaching of number concepts with a clear and simple explanation in alignment with the curriculum, supported by concrete examples; the inclusion of activities designed to help students better understand the relationships between numbers; and the provision of opportunities for students to develop strategies and problem-solving skills through targeted activities. Additionally, the use of supplementary resources that strengthen students' mathematical thinking skills and enhance their ability to relate numerical concepts to real-life situations is considered to contribute to students' development in the area of number sense.