Despite the current need for reliable and valid test instruments in different countries in order to monitor the sign language acquisition of deaf children, very few tests are commercially available that offer strong evidence for their psychometric properties. This mirrors the current state of affairs for many sign languages, where very little…

Argues that classical test theory cannot be used at the item level on "authentic" language tests. However, if the total score is derived by adding the scores of a number of different and independent parts, test reliability can be estimated. Suggests using the Classical Latent Additives model to examine test-part homogeneity. (Author/SED)