Abstract
The relationship between the self-efficacy of 23 High School students with intellectual
disability (ID) and their achievements in Mathematics was evaluated using a modified
version of the self-efficacy instrument developed by Joet, Bressoux and Usher (2011). Four
different number sense assessment tools were administered pre- and post- six months of
instruction to measure their Mathematics achievement. Relevant data analyses were carried
out with Minitab statistical software. While the mean self-efficacy was found to be about
65%, the correlation between self-efficacy and the mathematics achievements of students
was weak.