RESUMO

OBJECTIVE: Cohen's d conventional effect size cutoffs [small (0.2), medium (0.5), and large (0.8)] might not be representative of the reported distribution of effect sizes across the different areas of health. Effect size cutoffs might vary not only depending on the area of research, but also on the type of intervention and population. That is, they are context dependent. Therefore, we present strategies to redefine small, medium, and large effect size based on 25, 50, and 75th percentile, respectively. METHODS: We illustrate these techniques applying them to 72 effect sizes, derived from 65 randomized controlled trials described in a recent meta-analysis (10.1016/j.smrv.2021.101556) of improving sleep quality on composite mental health. Such percentiles are equally distanced from the average effect size as suggested by Jacob Cohen and checked for potential attenuation effects (via weight selection model) and outliers (via OutRules). RESULTS: new cutoffs for effect size distribution of -0.177, -0.329, and -0.557, for small, medium, and large effect size were found, respectively. applying Cohen's effect size thresholds (0.2, 0.5, and 0.8) for trials of improving sleep quality on composite mental health might over-estimate effect sizes compared to the real-world context, especially around medium and large effect sizes.

Assuntos

RESUMO

Effect sizes of school-based intervention are commonly described as small to moderate when using Cohen's conventional effect size cutoffs (small [0.2], medium [0.5], and large [0.8]). However, Jacob Cohen's rule of thumb might vary across different areas of research, nature of the intervention, and population, because effect sizes are context-dependent. Moreover, when planning research studies, minimum detectable effect sizes are used to calculate the sample size. In the present study, we investigate whether conventional effect size cutoffs (small [0.2], medium [0.5], and large [0.8]) represent the reported distribution of effect sizes in school-based anti-bullying intervention. To determine small, medium, and large effect sizes, we calculated the effect size distribution (ESD) using 50th percentile effect size (medium effect) of the distributions of effect sizes provided by a recent meta-analysis on school-based anti-bullying intervention. Also, the 25th and 75th percentile effects, as they are equidistant from the average effect size, were used redefining small and large effects, respectively. Results showed that 0.07, 0.123, and 0.227 represent small, medium, and large effect sizes in anti-bullying interventions. Our results indicate that Cohen's suggested effect size thresholds (0.2, 0.5, and 0.8) overestimate effect sizes when compared to the real-world context of school based anti-bullying interventions. We also propose sample sizes required to reliably detect small, medium, and large percentile effect sizes in anti-bullying interventions.

Assuntos

RESUMO

Is the assessment of motor milestones valid and scaled equivalently for all infants? It is not only important to understand if the way we use gross and fine motor scores are appropriate for monitoring motor milestones but also to determine if these scores are confounded by specific infant characteristics. Therefore, the aim of the study is to investigate the latent structure underlying motor milestone assessment in infancy and measurement invariance across sex, birth weight, and gestational age. For this study, the birth cohort data from the United Kingdom Millennium Cohort Study (MCS) was used, which includes the assessment of eight motor milestone tasks from the Denver Developmental Screening Test in 9-month-old infants (N = 18,531), depicting early motor development of the first children of generation Z. Confirmatory factor analyses showed a better model fit for a two-factor structure (i.e., gross and fine motor development) compared to a one-factor structure (i.e., general motor development), and multiple indicators multiple causes modeling revealed no differential item functioning related to sex, birth weight, and gestational age. The study provides support for the use of gross and fine motor scores when assessing motor milestones in infants-both boys and girls with different birth weights and of varying gestational ages. Further investigation into widely adopted assessment tools is recommended to support the use of valid composite scores in early childhood research and practice.