SAMPLE-SIZE EFFECTS ON TEMPORAL RELIABILITY OF LANGUAGE SAMPLE MEASURES OF PRESCHOOL-CHILDREN

The present study examined the temporal reliability of four quantitati ve measurements of operationally defined linguistic behaviors observed in a naturalistic setting. The measures of language production were c omputed using the Systematic Analysis oi Language Transcripts (SALT) S oftware from two 20-minute language samples obtained 3 to 14 days apar t for each of 20 preschool-aged children. Samples were edited to diffe rent sizes based either on duration (12 or 20 minutes) or on limits of the total number of complete and intelligible utterances (from 25 to 175 in increments of 25). lnadequate reliability was found for the lan guage sample measure, total number of words; hence, the validity of th is measure is questionable. in contrast, very high temporal reliabilit y coefficients (r >.92) were obtained for the language sample measures of number of different words, mean length oi utterance in morphemes, and mean sentence length in morphemes when derived from a large number (greater than or equal to 175) of complete and intelligible utterance s. The temporal reliability of these measures reached acceptable level s, no: only for research purposes, but for diagnostic purposes as well .