Sources of variability in speechreading sentences: a generalizability analysis.

Generalizability theory (Cronbach, Gleser, Nanda, & Rajaratnam, 1972) was used to estimate the percentage of variance explained by three sources of variability in speechreading sentences: the subject, the talker, and the sentence materials. Videodisc recordings of the 100 CID Everyday Sentences (Davis & Silverman, 1970), spoken by a male and a female talker, were presented to 104 subjects with normal hearing. For performance on individual sentences (total number of words correct), the most important systematic sources of variability were the sentence (26.3%), the speechreader (10.5%), the talker (4.9%), and the interaction of talker and sentence (5.1%). Residual error accounted for 51.2% of the variance. Generalizability functions are presented, as a function of test length, for five models of test administration and interpretation. For 10-, 50-, and 100-item lists, generalizability is predicted to be .70, .92, and .96, respectively, for a single talker. Psychometric characteristics of these recordings of the CID sentences are also presented.