FIGURE 8.15 Relation between 8th-graders’ number-line estimation accuracy and their math achievement test scores Accuracy of number-line estimation is closely related to overall mathematics achievement. These data show the relation between middle school children’s math achievement test scores and the accuracy of their estimates of fraction magnitudes. Similar relations have been found between elementary school children’s math achievement test scores and their estimates of whole-number magnitudes. The correlation is negative, because estimates that are less distant from numbers’ correct locations indicate greater knowledge of the numerical magnitudes. (Data from Siegler, Thompson, & Schneider, 2011)