Abstract
The purposes of this study were to investigate second graders’ number-line estimation ability as well as to explore the relationship between their number-line estimation ability and mathematical achievement. The participants in this study were 137 second graders of an elementary school in Taoyuan City, Taiwan, and a number-line estimation task (including number-to-position and position-to-number tasks) and a mathematical achievement test were used as examining tools. The results of this study are as follows. First, on a 0-100 number line, the second graders’ estimates fit the linear model. Significant differences were observed between the number-to-position and position-to-number task results. The students’ estimation ability in the position-to-number task was superior to that in the number-to-position task. Second, significantly positive correlations between number-line estimation ability and mathematical achievement were observed. Finally, the ability to complete a number-to-position task explained 13% of the variance in the students’ mathematical achievement; thus, it can predict students’ mathematical achievement.