Improving primary school second grade students' number sense levels on the basis of ADDIE instructional design

The number sense has an important place in individuals' mathematical calculations, mental skills, education, and all periods of their daily lives. Much research has been done on the number sense in mathematics education; Individuals' strengths or weaknesses in number sense are revealed. In the studies conducted, the levels and difficulties experienced by individuals in number sense were generally determined. The problems revealed in the number sense in studies have not been solved adequately. In researches, the problems revealed in the number sense have not been solved adequately. The aim of the study was determined to improve the level of number sense with the instructional design of second grade primary school students in order to overcome the problems caused by not improving their number sense. For this purpose, action research, one of the qualitative research methods, was used in the study conducted with 20 students in a village primary school in Yozgat in the second semester of the 2018-2019 academic year. In accordance with this purpose, action research which is one of the qualitative research methods was used in the study conducted with 20 students in a village primary school in Yozgat in the second semester of the 2018-2019 academic year. In determining the student group, purposeful sampling method, which is one of the qualitative research approaches, non-random sampling types, was used. The student group was determined purposeful sampling method, which is one of the qualitative approaches that are non-random sample types, was used. Instructional design model, academic achievement test and number sense test were developed in line with expert opinions to measure students' number sense level. In determining the deficiencies of the students in the field of number sense in questions and components, determining the strategies they use while solving the problems, and evaluating the action steps of the instructional design, the item pool that was created in line with the instructional objectives was presented to the expert opinion and the academic achievement test was developed. In addition, in the research process, four number sense components were taken as basis in all processes of academic achievement test, number sense test and research action steps. The answers given to the questions in the number sense test used in the academic achievement test and in the process of applying the action step were analyzed in terms of both the accuracy and the solution strategy used (number sense strategy / rule-based strategy), and the academic achievement test and number sense test score were calculated. In order to examine the strategies used in the number sense test in depth, a total of 54 interviews were conducted with six students at each action step after nine action steps, according to their number sense scores. In order to analyze the strategies thoroughly used in the number sense test, after the nine action steps, a total of 54 interviews were conducted with six students in each action step according to their number sense scores. During the interviews, semi-structured interviews were made with the students, and the questions selected from the number sense test were asked to the students, and the students were asked to explain the solutions they used to solve these questions. Data were collected through observation, interview, academic achievement test, number sense test and student activity book during the research process. The analysis of the data was done by inductive method, the analysis of the data obtained from the observations and interviews was carried out with NVivo 12 software, it was observed that there was a significant improvement in the students' number sense levels in both written and verbal responses. In addition, the data obtained from the pretest and posttest (academic achievement test) was analyzed by the Wilcoxon signed rank test, and when the mean rank and totals of the difference scores in the students' sense of number were taken into account, it was seen that this difference was in favor of the positive ranks, that is, the posttest score. The relationship between the participants' academic achievement scores, semester grade averages, and second term grade point averages was analyzed with the Pearson product moment correlation coefficient (r). According to these findings, a positive, high and significant relationship was found between students' achievement in the academic achievement test and both their semester grade average and their second term success. Keywords: Mathematics, Number Sense, Number Sense Strategy, Rule Based Strategy, Instructional Design and Model.