When individuals are given tests that are too hard or too easy, the resulting scores are likely to be poor estimates of their performance. To get valid and accurate test scores that provide meaningful results, one should use functional-level testing (FLT). FLT is the practice of administering to an individual a version of a test with a difficulty…

A series of computer simulations was run to measure the relationship between testlet validity and the factors of item pool size and testlet length for both adaptive and linearly constructed testlets. Results confirmed the generality of earlier empirical findings of H. Wainer and others (1991) that making a testlet adaptive yields only marginal…