The correct answer is: b) effect sizes Meta-analysis is a statistical tool that evaluates effect sizes across multiple studies. It involves computing an effect size across all of the studies, which involves extracting effect sizes and variance measures from various studies. The other options (a, c, d) are not typically evaluated across multiple studies using meta-analysis. Meta-Analysis: Evaluating Across Multiple Studies Meta-analysis is the statistical combination of the results of multiple studies addressing a similar research question. An important part of this method involves computing an effect size across all of the studies . Meta-analyses are integral in supporting research grant proposals, shaping treatment guidelines, and influencing health policies. They are also pivotal in summarizing existing research to guide future studies, thereby cementing their role as a fundamental methodology in metascience . Evaluation Criteria for Meta-Analysis Evaluation criteria for meta-analysis include the need for the following: Clear identification of the problems under study Active effort to include all available studies Assessment of publication bias Identification of data used Selection and coding based on theoretical framework, not convenience Detailed documentation of coding Use of multiple raters to assess coding, including assessment of interrater reliability Assessment of comparability of the cases, controls, and circumstances in the studies analyzed Considera