To ensure comparability of tests from one test administration to the next, large-scale assessment programs use a process of test score equating. Without such methods for building equivalent tests, it would be impossible to measure changes in achievement over time. Traditionally, equated tests have been used to measure year-to-year changes for different students in the same grade. Have this year’s third graders performed better in reading than last year’s third graders? Increasingly, however, there is interest in measuring growth in achievement, which requires linking different tests across grades. How much growth did fourth graders show compared to their achievement last year in third grade? Linking is the term used to refer to several types of statistical methods used to establish a relationship between the score scales from two tests so that results from one test can be compared to results on another test.