Stepped-Wedge Clinical Trial Analysis and Power Simulation R package stepwedgepower version 0.1.3 Provides reusable functions for aggregated cluster-period data, mixed-effects analysis, and simulation-based power and type I error evaluation in stepped-wedge cluster randomized trials. The design and mixed-effects analysis follow Hussey and Hughes (2007) <doi:10.1016/j.cct.2006.05.007>. Intraclass correlations for binary outcomes are converted to logistic-normal random-intercept standard deviations following Eldridge, Ukoumunne and Carlin (2009) <doi:10.1111/j.1751-5823.2009.00092.x>. Monte Carlo uncertainty in estimated power is summarized using the exact binomial interval of Clopper and Pearson (1934) <doi:10.1093/biomet/26.4.404>. The simulation engine supports sequence-specific baseline risks, cluster random effects, direct intraclass-correlation specification, Monte Carlo uncertainty intervals, and model-fitting diagnostics. Applied physician and specialty helpers are retained for backward compatibility and for an example health-services workflow. Software Imports: lme4 Suggests: testthat (>= 3.0.0), knitr, rmarkdown Lin (Amanda) Li <amandali14124277@gmail.com> Comprehensive R Archive Network (CRAN) Lin (Amanda) Li [aut, cre], Florin Vaida [aut] (degree: PhD) MIT + file LICENSE (https://CRAN.R-project.org/package=stepwedgepower/LICENSE) 2026-07-13 application/tgz https://CRAN.R-project.org/package=stepwedgepower doi:10.32614/CRAN.package.stepwedgepower