Tense Marking in the General Kindergarten Population: Is there Evidence of Bimodal Distribution?
Weiler, Brian Kenneth
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2016-03-30
Abstract
Tense marking at the point of school entry, that is, kindergarten, has been hypothesized to follow a bimodal distribution. Under this hypothesis, it is predicted that most children exhibit tense marking skills at or near the upper end of proficiency whereas some children demonstrate notably reduced proficiency. Due to this separation of skill level, kindergarten tense marking is considered a clinical marker for language impairment. The purpose of this study was to test the validity of a bimodal distribution of tense marking in a population-based sample of kindergarten students. The Test of Early Grammatical Impairment (TEGI) Screening Test was administered to three-quarters of the kindergarten students attending a school district of Mainstream American English speakers. Results revealed a distribution of TEGI Screening Test Scores that deviated significantly from normality. Cluster analysis indicated a best-fitting two-cluster solution that, upon inspection, generally aligned with bimodal-distribution expectations for typical and language-impaired classification prevalence rates and threshold values. Cross validation of child cluster membership to a reference standard for a subsample of participants offered further, albeit preliminary, evidence in support of the discriminant validity of assessing tense marking for the purpose of identifying language impairment in the general kindergarten population.