Selecting an appropriate statistical test remains a persistent challenge for students and novice researchers, as it requires coordinating multiple methodological conditions and decision criteria. Existing visual tools often provide direct recommendations but do not make the underlying decision pathway explicit and frequently lack empirical validation. This study presents the development and expert validation of the Velarde-Camaqui Diagram, a visual decision-support tool designed to guide users through inferential statistical test selection using a structured, sequential approach. A mixed-methods design was conducted with 14 PhD-level experts in education and statistics. Results showed high agreement across clarity, coherence, relevance, and usability (85-100%). Content validity was supported by an overall Aiken's V of.89. Qualitative findings highlighted strengths in conceptual clarity and pedagogical usability, while identifying opportunities for improving visual structure. The diagram contributes by making the inferential decision process explicit, integrating both parametric and non-parametric tests, and offering a multilingual, accessible format. These features position it as both a decision-support system and a pedagogical scaffold. Future research should examine its impact on learning outcomes and statistical decision-making in applied contexts.
