The Study aimed at determining the effectiveness of a statistical unit based on mathematical connections in the development of statistical thinking and achievement among 10th grade students. The sample of the study consisted of (51) female students from Lubaba Bint Al-Harith School. The sample was divided into two groups: experimental group consisted of (25) students, and a control group consisted of (26) students. The two groups were equivalent at statistical thinking and achievement prior to the experiment. To analyze the data the researcher used the arithmetic mean, standard deviations, and t-test and the study reached the following results: - There is a statistical significant differences at the level of (a = 0.05) among the middle-grades students in grades dimensional test for the experimental group. - There is a statistical significant difference at the level of (a - 0.05) among the middle-grades students to test the statistical dimensional thinking in favor of the experimental group. In light of these results the researcher recommended the need to address the life problems in general and mathematics and statistics in particular, because of the importance of math and its benefits and encouragement for students to take care of its knowledge and skills.