Construct Two-Phase Experimental Designs with Correlated Errors R package TwoPhaseCorR version 1.1.1 Tools for constructing and analyzing two-phase experimental designs under correlated error structures. Version 1.1.1 includes improved efficiency factor classification with tolerance control, updated plot visualizations, and improved clarity of the results. The conceptual framework and the term two-phase were introduced by McIntyre (1955) <doi:10.2307/3001770>). Software Imports: MASS, Matrix, dplyr, ggplot2 Akhilesh Jha <jha.akhilesh09@gmail.com> Comprehensive R Archive Network (CRAN) Akhilesh Jha [aut, cre], Cini Varghese [aut], Seema Jaggi [aut], Eldho Varghese [aut], Mohd Harun [aut], Med Ram Verma [aut] GPL-3 2025-07-29 application/tgz https://CRAN.R-project.org/package=TwoPhaseCorR doi:10.32614/CRAN.package.TwoPhaseCorR