Age at menarche is critical in research and clinical settings, yet there is a dearth of studies examining its reliability in adolescents. We examined age at menarche during adolescence, specifically, (a) average method reliability across 3 years, (b) test-retest reliability between time points and methods, (c) intraindividual variability of…

Researchers often have expectations about the research outcomes in regard to inequality constraints between, e.g., group means. Consider the example of researchers who investigated the effects of inducing a negative emotional state in aggressive boys. It was expected that highly aggressive boys would, on average, score higher on aggressive…

Used growth curves and dynamic-systems modeling to examine early lexical and grammatical development of one male child. Found that lexical development described a pattern of logistic growth. Plural growth began after reaching a threshold in vocabulary size. Lexical growth slowed as plural growth increased, and increased when plural use reached…