Power of Interrupted Time Series (ITS) Studies R package PITS version 0.1.0 Provides tools for estimating the statistical power of Interrupted Time Series (ITS) designs, with a focus on healthcare applications. The package supports prospective power calculations before a study begins, and retrospective assessments of whether a completed study was adequately powered. It includes functions to estimate nuisance parameters (baseline, residual standard deviation, autocorrelation) from data observed before the intervention, and to estimate power via Monte Carlo simulation for single-site and multi-site designs. Utility functions for design optimisation sweeps and publication- ready plots are also provided. Software Depends: R (>= 4.0.0) Imports: nlme, stats, graphics, grDevices, utils Suggests: knitr, rmarkdown, testthat (>= 3.0.0) David de Lorenzo <drdaviddelorenzo@gmail.com> Comprehensive R Archive Network (CRAN) David de Lorenzo [aut, cre] (ORCID: <https://orcid.org/0000-0003-2042-0961>, affiliation: UCL Great Ormond Street Institute of Child Health, London, UK; Neotree, London, UK (https://neotree.org/)) MIT + file LICENSE (https://CRAN.R-project.org/package=PITS/LICENSE) 2026-06-30 application/tgz https://CRAN.R-project.org/package=PITS doi:10.32614/CRAN.package.PITS en-GB