Methodological Issues in Group-Matching Designs:   Levels for Control Variable Comparisons and Measurement Characteristics of Control and Target Variables

Abstract

Group-matching designs are commonly used to identify the diagnosis-specific characteristics of children with developmental disabilities. In this paper, we address three issues central to the use of this design. The first concerns the alpha level to be used for considering groups to be matched on the control variable(s). The second involves the measurement characteristics of the control and target variables. We discuss the properties of standard scores, raw scores, and age equivalents and argue against the use of age equivalents. In addition, we consider the appropriateness of the commonly made prediction that groups that are matched for a control variable such as language ability or nonverbal reasoning ability but are not matched for chronological age should perform at equivalent levels on the target variable. Finally, we discuss issues related to the interpretation of significant between-group differences on the target variable, assuming groups are well-matched on the control variables, and describe the benefits of a method that focuses on characterizing a disorder on a case-by-case basis and then aggregating the cases, using the measures of sensitivity and specificity from signal detection theory.

Repetitive and Stereotyped Behaviors in Children with Autism Spectrum Disorders in the Second Year of Life

“…The demographic characteristics of the three groups are presented in Table 1 and these indicate that all 3 groups were well-matched on mother's and father's education and mother's age, using the criterion p-value of > .50 on tests of group differences for the purposes of matching (Mervis & Klein-Tasman, 2004). This suggests that the groups were comparable on socioeconomic status.…”

A Longitudinal Study of Cognitive Abilities in Williams Syndrome

“…In order to evaluate strengths and weaknesses over time in WS, it is important that standard scores (based on the same normative reference group) are used, as raw scores are not comparable across tasks or across different age groups (Baron, 2004;Mervis & Klein-Tasman, 2004).…”

Online Action Monitoring and Memory for Self-Performed Actions in Autism Spectrum Disorder

“…Matching for VIQ is essential in studies of cognitive function in individuals with ASD. It is possible that differences between groups in this respect can potentially entirely explain between-group differences in Millward et al,'s experimental task (see Mervis & Klein-Tasman, 2004). …”