ABSTRACT
Many currently available effect size measures for mediation have limitations when the predictor is nominal with three or more categories. The mediation effect size measure υ was adopted for this situation. A simulation study was conducted to investigate the performance of its estimators. We manipulated several factors in data generation (number of groups, sample size per group, and effect sizes of paths) and effect size estimation [different R-squared (R 2) shrinkage estimators]. Results showed that the Olkin-Pratt extended adjusted R 2 estimator had the least bias and the smallest MSE in estimating υ across conditions. We also applied different estimators of υ in a real data example. Recommendations and guidelines were provided about the use of this estimator.
ABSTRACT
Pediatric irritability can be highly impairing and is implicated in adverse outcomes. The phasic component, characterized by temper outbursts, is a frequent impetus to seek treatment. This study tested whether a previously described anger-distress model of tantrums applies to an outpatient sample of school-age children with clinically impairing temper outbursts (TO; 5.0-9.9 years; N = 86), and examined the clinical relevance of resulting factors through associations with measures of psychopathology, and differences between children with TO and two groups without: children with ADHD (n = 60) and healthy controls (n = 45). Factor analyses established a three-factor model: High Anger, Low Anger, Distress. These factors had unique associations with measures of irritability, externalizing problems, and internalizing problems in the TO group. Additionally, an interaction between groups and outburst factors emerged. Results provide evidence for the presence and clinical utility of the anger-distress model in children's outbursts and suggest avenues for future pediatric irritability research.
