ABSTRACT
The measurement of vocabulary gains is probably the most common type of vocabulary measurement, both in language classrooms as well as in research studies. Any intervention study will have to provide robust measurement to demonstrate whether a particular treatment was or was not effective. However, this also seems one of the most challenging types of measurement, as there are a number of critical issues that require careful consideration. This chapter will discuss three of these.
First, the research design itself is highlighted as a central concern. Issues regarding the need for control groups, pretests and immediate and/or delayed posttests, testing effects, and the spacing of delayed posttests are outlined. Second, the type of test used for measuring lexical gains is established as an important consideration. It is described when it is more appropriate to use achievement tests (with items corresponding to the vocabulary focused on in the treatment) and when it is more suitable to employ tests that measure changes in overall breadth of vocabulary knowledge. It also problematizes the sensitivity and validation of these instruments and illustrates these issues on developmental vocabulary scales. Third, concerns related to selection of target words and test formats for these instruments are discussed as they pertain to score interpretation and different aspects of word knowledge that could be measured.
