Inspecting a mathematics textbook might give the impression that, in order to be competent with decimal numbers, all that students need to do is remember a few rules for placing the decimal point, and otherwise perform operations with decimal numbers as if they were whole numbers. Yet international studies show that many students do not make this apparently small step with ease.
This thesis reports on a longitudinal study of student understanding of decimal notation. Over 3000 students completed nearly 10000 tests over a 4-year period; the diagnostic test used in this study was created by...