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Identifying change at the individual level is an important goal for researchers, educators, and clinicians. We present a set of statistical procedures for identifying individuals who depart from a normative change. Using Latent Change Scores models (LCS), we illustrate how the Individual Likelihood computed from a statistical model for change ("IL") and from an alternative unrestricted model ("ILsat") can be used to identify atypical trajectories in situations with several measurement occasions. Using LCS and linear regression, we also show how the observed and latent change residuals can be used to identify atypical individual change between 2 measurement occasions. We apply these methods to a measure of general verbal ability (from WISC-R), from a large sample of individuals assessed every 2 years from Grade 1 to 9. We demonstrate the efficiency of these techniques, illustrate their use to identify individual change in longitudinal data, and discuss potential applications in developmental research.

We systematically assessed the relationships between growth of four components of verbal ability--Information, Similarities, Vocabulary, and Comprehension subtests of the Wechsler Intelligence Scale-Revised--and longitudinal growth from Grades 1 to 9 of the Woodcock-Johnson Psycho-Educational Battery Passage Comprehension subtest while controlling for Word Identification and Word Attack, using multilevel growth models on a sample of 414 children. Growth was assessed over all grades (1-9), and separately for early grades (1-5) and later grades (5-9). Over all grades, growth in Word Identification had a substantial standardized loading to Passage Comprehension, and all four verbal abilities had smaller, but significant standardized loadings to Passage Comprehension (p < 0.05), with Information and Vocabulary having slightly higher loadings than Similarities and Comprehension. For early grades, results were similar to the overall results, with the exception of Vocabulary, which had a nonsignificant loading to Passage Comprehension. For later grades, Word Identification again had the largest, but substantially smaller standardized loading on Passage Comprehension and standardized loadings of all four verbal abilities were statistically significant with Vocabulary and Wechsler Intelligence Scale for Children-Revised (WISC-R) Comprehension having appreciably higher loadings than in the previous analyses. Conversation- and interaction-based intervention and instruction in oral language in general, and vocabulary in particular throughout early childhood and continuing throughout the school years, combined with evidence-based instruction that systematically develops the skills of phonologic awareness, decoding, word reading, fluency, and comprehension in school, may provide a pathway to reducing the achievement gap in reading.

Simulated data were used to demonstrate that groups formed by imposing cut-points based on either discrepancy or low-achievement definitions of learning disabilities (LD) are unstable over time. Similar problems were demonstrated in longitudinal data from the Connecticut Longitudinal Study, where 39% of the children designated as having LD in Grade 3 changed group placement with repeated testing in Grade 5. These results show that the practice of subdividing a normal distribution with arbitrary cut-points leads to instability in group membership. Approaches to the identification of children as having LD based solely on individual test scores not linked to specific behavioral criteria lead to invalid decisions about individual children. Low-achievement definitions are not a viable alternative to IQ-discrepancy definitions in the absence of other criteria, such as the traditional exclusions and response to quality intervention. If we accept the premise of multiple classes of low achievers, then we must develop identification systems that are valid and abandon systems whose only merits are their historical precedence and convenience.

Simulated data were used to demonstrate that groups formed by imposing cut-points based on either discrepancy or low-achievement definitions of learning disabilities (LD) are unstable over time. Similar problems were demonstrated in longitudinal data from the Connecticut Longitudinal Study, where 39% of the children designated as having LD in Grade 3 changed group placement with repeated testing in Grade 5. These results show that the practice of subdividing a normal distribution with arbitrary cut-points leads to instability in group membership. Approaches to the identification of children as having LD based solely on individual test scores not linked to specific behavioral criteria lead to invalid decisions about individual children. Low-achievement definitions are not a viable alternative to IQ-discrepancy definitions in the absence of other criteria, such as the traditional exclusions and response to quality intervention. If we accept the premise of multiple classes of low achievers, then we must develop identification systems that are valid and abandon systems whose only merits are their historical precedence and convenience. [ABSTRACT FROM AUTHOR]

This paper attempts to model the development of children's reading skills using the negative exponential curve with mixed effects model. The model describes the nature of growth in children's reading skills and accounts for intra-individual and inter-individual variations. In addition, we propose methods including cross-validation, regression, and graphing to determine an appropriate curve for the data, to find good initial values for parameters, and to select potential covariates. We illustrate with an example that motivated this research: a longitudinal study of academic reading skills from grade 1 to grade 12 in Connecticut public schools. [ABSTRACT FROM AUTHOR]

Compares two commonly employed definitions of reading disability using the Connecticut Longitudinal Study cohort, a sample survey of Connecticut schoolchildren followed from kindergarten. Cognitive and behavioral characteristics of children; Notion of an unexpected inability or failure to read; Operational criteria for reading disability.

Objectives: To determine if differences between dyslexic and typical readers in their reading scores and verbal IQ are evident as early as first grade and whether the trajectory of these differences increases or decreases from childhood to adolescence., Study Design: The subjects were the 414 participants comprising the Connecticut Longitudinal Study, a sample survey cohort, assessed yearly from 1st to 12th grade on measures of reading and IQ. Statistical analysis employed longitudinal models based on growth curves and multiple groups., Results: As early as first grade, compared with typical readers, dyslexic readers had lower reading scores and verbal IQ, and their trajectories over time never converge with those of typical readers. These data demonstrate that such differences are not so much a function of increasing disparities over time but instead because of differences already present in first grade between typical and dyslexic readers., Conclusions: The achievement gap between typical and dyslexic readers is evident as early as first grade, and this gap persists into adolescence. These findings provide strong evidence and impetus for early identification of and intervention for young children at risk for dyslexia. Implementing effective reading programs as early as kindergarten or even preschool offers the potential to close the achievement gap., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The authors applied linear dynamic models to longitudinal data to examine the dynamics of reading and cognition from 1st to 12th grade. They used longitudinal data (N=445) from the Connecticut Longitudinal Study (S. E. Shaywitz, B. A. Shaywitz, J. M. Fletcher, & M. D. Escobar, 1990) to map the dynamic interrelations of various scales of the Wechsler Intelligence Scales for Children--Revised (i.e., Full, Performance, and Verbal) and specific markers of the Woodcock-Johnson Psycho-Educational Battery--Revised reading cluster (i.e., Letter-Word ID, Decoding, and Comprehension). The results of these analyses indicate that (a) there is a positive dynamic relation between reading and cognition across the selected age range; (b) this dynamic relation is symbiotic, with positive influences in both directions; (c) the influence from cognition to reading is stronger when considering the Wechsler Intelligence Scales for Children Performance--Revised Performance scale and weaker with the Verbal scale; (d) when examining the different Reading subtests, the influences from cognition are more apparent for Letter-Word ID and Comprehension and are less perceptible for Decoding; and (e) the dynamics of reading and cognition appear to be of stronger magnitude during 1st to 3rd grade, less strong during 4th to 8th grade, and weaker from 9th to 12th grade., ((c) 2007 APA.)