Assessing qualitative data richness and thickness: development of an evidence-based tool for use in qualitative evidence synthesis Short running title: A data thickness/richness assessment tool

This paper introduces version one of an assessment tool developed to address the challenges posed by the assessment of data thickness and richness in primary qualitative studies for Qualitative Evidence Syntheses (QES). The tool has been in development since 2014. Three pilot versions from three review teams have been used in six Cochrane reviews. Key members from the original three review teams came together to create a consensus-based definitive version 1 of the tool for publication. Four review authors piloted the version 1 tool. The definitive version 1 assessment tool consists of two components: assessing the thickness of contextual data and assessing the richness of conceptual data. A sliding scale with four points is used to rate these aspects, offering nuanced and qualitative judgments. The accompanying guidance emphasizes the importance of assessing data that addresses the review question. Paragraph locked by Heather Melanie R Ames The paper provides guidance on how to apply the tool, emphasizing the importance of reaching a consensus among review authors, and fostering a shared understanding of what constitutes rich and thick data in the context of the review. The potential challenges related to the time and resource constraints of this additional review process are acknowledged. Version 1 of the data thickness/richness assessment tool represents a significant development in QES methodology, filling a critical gap in tools for evaluating the richness of conceptual data and the level of contextual detail in primary qualitative studies. It enhances the transparency and rigor of the sampling process and offers valuable insights for assessing the thickness and richness of data in primary qualitative studies that addresses the review requestion, objectives and context as specified in the review protocol. The authors invite feedback from the research community to further test, refine and improve this tool based on wider user experiences.