Meaningful Associations Redux: Quantifying and interpreting effect size in the context of the Adolescent Brain and Cognitive Development Study.

The Adolescent Brain Cognitive Development (ABCD) Study represents a pioneering initiative aimed at unraveling the complexities of behavioral and neural development in youth. In this paper, we address the multifaceted challenges inherent in extracting meaningful insights from the extensive data compiled by the ABCD initiative. Our focus is on advocating for the adoption of best practices in reproducible research methodologies and result reporting. Central to this discourse is a meticulous examination of effect sizes within the expansive ABCD dataset. We describe the hurdles associated with the transition from conventional small-sample studies to the unprecedented opportunities, alongside concomitant dilemmas, presented by large-sample research endeavors. To assess the true impact and relevance of findings from the ABCD study, we call on researchers to move beyond a primary focus on statistical significance, and to instead prioritize the more compelling domains of practical and clinical significance. Additionally we provide guidance on how to contextualize, visualize, and scrutinize ABCD results to distinguish meaningful findings from trivial (albeit reliable) effects. In turn, probing findings in this manner yields a broader, richer, and more compelling portrait of the "significance" of observed connections and contributes substantively to the refinement of research practices within the domain of adolescent brain and cognitive development.