PRDA: An R package for Prospective and Retrospective Design Analysis

The paper describes the PRDA package available at https://cran.r-project.org/web/packages/PRDA/ . PRDA is an R package performing prospective or retrospective design analysis (see Gelman & Carlin, 2014 and Altoè et al., 2020) to evaluate inferential risks (i.e., power, Type M error, and Type S error) in a study considering Pearson’s correlation between two variables or mean comparisons (one-sample, paired, two-sample, andWelch’st-test). Prospective Design Analysis is performed in the planning stage of a study to define the required sample size to obtain a given level of power. Retrospective Design Analysis, instead, is performed when the data have already been collected to evaluate the inferential risks associated with the study. PRDA, additionally, offers the possibility to conduct a prospective/retroprospective design analysis taking into account for the uncertainty about the hypothetical value of effect size. In fact, hypothetical effect size can be defined as a single value according to previous results in the literature or experts indications, or by specifying a distribution of plausible values.