Uses of Rasch scaling in the measurement of cognitive development and growth.

This report describes two types of findings: (a) the consistency between two major cognitive tests in terms of their developmental scales based on item-response theory, and (b) the initial development of ideas and methods for the revival of the classic concept of ratio IQ. The ratio IQ (e.g., Stanford-Binet, 1937) was formed by the division of mental age (derived from test performance) by chronological age multiplied by 100. Following a multitude of criticisms about the scaling qualities of the ratio IQ, it was mostly abandoned by the major intelligence batteries, beginning with the Wechsler scales in the 1940's, in favor of standard scores. This study presents a new approach to age equivalence scores as a basis for mental age, and the calculation of ratio IQ, based on Rasch-model item response theory. The new ratio IQ was compared statistically with standard-score IQ (mean 100, SD 15) from the Leiter International Performance Scale--Revised (Leiter-R) and from the Woodcock-Johnson Psychoeducational Battery--Revised (WJ-R). The essential element of the new ratio IQ is the W-scale, a Rasch-based score employed in the WJ-R and in the Leiter-R. Mental age was estimated from the W-scale estimate of ability and chronological age from a W-scale age equivalence for each month of age. Statistical results showed a highly similar growth curve for the W-scale scores on the Leiter-R and the WJ-R, even though the two scales have different content and standardization samples. Also, high correlations were found between the new ratio IQ and standard-score IQ (e.g., correlations ranging from .87 to .95 depending on age range). Criterion-related evidence of validity was found in the correlation of .82 between the new ratio IQ and the Wechsler Intelligence Scale for Children--Third Edition (WISC-III) standard-score IQ and in correlations with achievement-test scores. Finally, the ratio IQ showed predictable mean differences between groups of children with typical cognitive ability, cognitive delay levels of performance and giftedness. The standard deviation of the new ratio IQ was somewhat variable across age groups, however, so new interpretive guidelines would be needed if the new index is to employed in published tests. Implications of the scaling methods are discussed.

Nonverbal intellectual assessment of Hispanic and speech-impaired adolescents.

A comprehensive new nonverbal cognitive battery (Leiter-R) was given to examine the nonverbal cognitive performance of adolescents, ages 11 to 21 from majority and nonmajority (Hispanic) ethnic backgrounds. A total of 258 Euro-American (non-Hispanic) and 62 Hispanic adolescents composed the ethnic-contrast samples (81% Euro-American vs 19% Hispanic). Also, the study used the Leiter-R to contrast the cognitive performance of speech-impaired adolescents with typical children, ages 11 to 15. There were 203 without and 21 with speech impairments. The speech-impaired contrast sample was comprised of Euro-American (75%) and African-American (25%). This sampling provided direct comparisons equated for ethnicity. Small effect size differences (.11) were found on 3 of the 10 nonverbal subtests of the Visualization and Reasoning battery of the Leiter-R between Euro-American and Hispanic adolescents and the speech-impaired contrasts (effect size difference of .17). The Leiter-R exhibited potential for ethnic fairness in assessment. Further, promise for unbiased assessment of speech-impaired adolescents was provided. Fairness of assessment was especially evident for speech-impaired adolescents on the "visual" subtests of Picture Context, Matching, and Form Completion.

Sequence comparison methodology for the analysis of movement patterns in infants and toddlers with and without motor delays.

In an attempt to quantify the theoretical construct quality of movement, a set of measurable constructs were identified by subject matter experts, and a scale (the Toddler and Infant Motor Evaluation [TIME]) incorporating those constructs was developed and pilot tested. Sequence comparison data analysis methodology was examined for its applicability to examining series of movements. The study sample consisted of randomly selected children from a pilot edition of the scale. Because research indicates that specific individual positions cannot provide an accurate indication of the normalcy or dysfunction of the motor performance of infants and toddlers, this study researched the ability of series of movement positions in each of five postures (prone, supine, sit, quadruped, and stand) to discriminate between normal and atypical motor development. It was hypothesized that children with motor delays would demonstrate different sequences of movements than children without motor delays. The findings confirmed the hypothesis, because in this sample there was a significant difference in the performance of children with developmental delays in motor abilities compared with that of children who had normal movement abilities. Children with motor delays had poorer mobility, which was characterized by fewer transitions between movement patterns than children with normal motor abilities.