This report illustrates procedures of item construction for addition and subtraction examples involving decimal fractions. Using a procedural network of skills required to solve such examples, an item characteristic matrix of skills analysis was developed to describe the characteristics of the content domain by projected student difficulties. Then 24-item tests were constructed for addition and subtraction with decimals. Pre- and posttest versions of each were administered to more than 100 junior high school students. After the pretest, each student was provided with some remediation geared to the particular "bugs" (persistent errors); then the posttest was given. A prediction of item dominance based on test characteristics is compared with item dominance determined from an item relational structure analysis of the data. (MNS)