<i>SampleSavvy:</i> Evaluating a Web Tool for Easier Sample Size Planning

Determining an appropriate sample size is a challenging part of study design. Although established tools such as G*Power are widely used, they can be difficult for users without strong statistical backgrounds. To address this challenge, we developed SampleSavvy, a web-based tool that guides users through key power-analysis parameters and shows how these decisions influence sample size estimates. This tool provides an interactive, step-by-step interface for specifying effect size, alpha, and power while allowing real-time exploration. We evaluated its usability through a think-aloud study with seven participants who had varying experience levels. Results show that participants perceived SampleSavvy as more intuitive and easier to use than G*Power, particularly because of its structured workflow and clear guidance. Participants also identified future improvements, including expanded statistical test options and more flexible input methods. These findings suggest opportunities for user-centered tools that support sample size planning and research design.