Power Simulation for Sequential Analyses and Multiple Hypotheses R package POSSA version 0.6.5 Calculates, via simulation, power and appropriate stopping alpha boundaries (and/or futility bounds) for sequential analyses (i.e., group sequential design) as well as for multiple hypotheses (multiple tests included in an analysis), given any specified global error rate. This enables the sequential use of practically any significance test, as long as the underlying data can be simulated in advance to a reasonable approximation. Lukács (2022) <doi:10.21105/joss.04643>. Software Depends: R (>= 3.6.0) Imports: data.table, methods Suggests: testthat (>= 3.0.0), knitr, rmarkdown, faux Gáspár Lukács <lkcsgaspar@gmail.com> Comprehensive R Archive Network (CRAN) Gáspár Lukács [aut, cre] BSD_2_clause + file LICENSE (https://CRAN.R-project.org/package=POSSA/LICENSE) 2025-08-21 application/tgz https://CRAN.R-project.org/package=POSSA doi:10.32614/CRAN.package.POSSA