Testlet Response Theory

A testlet or an item bundle refers to a group of interrelated items presented as a single unit. Often, a testlet consists of several items following a single stimulus. It is a commonly used test construction unit in large-scale assessments and often provides a context or situation for assessing knowledge, skills, and ability. Passages in reading comprehension tests, scenarios in science tests, and graphs and/or tables in math tests are such examples in practice. When items are constructed around such a common stimulus, items associated with the same stimulus are connected by the common context. Item connection or clustering may affect an examinee’s performance on those items due to the common contextual effects. Thus, local item dependence (LID) or testlet effects may be induced. When ...