An R package implementing hierarchical item response theory (IRT) models where both the mean and the variance of latent preferences (ability parameters) may depend on observed covariates (Zhou 2018). The current implementation includes both the two-parameter latent trait model for binary data and the graded response model for ordinal... Read more about hIRT: Hierarchical Item Response Theory Models
In causal mediation analysis with multiple causally ordered mediators, a set of path-specific effects are identified under standard ignorability assumptions. This package implements an imputation approach to estimating these effects along with a set of bias formulas for conducting sensitivity analysis (Zhou and Yamamoto <doi:10.31235/osf.io/2rx6p>). It contains two main functions: paths() for estimating path-specific effects and sens() for conducting sensitivity analysis. Estimation uncertainty is quantified using the nonparametric... Read more about paths: An Imputation Approach to Estimating Path-Specific Causal Effects
This packages implements the regression-with-residuals (RWR) approach to causal mediation analysis, allowing for post-treatment confounding of the mediator-outcome relationship (Zhou and Wodtke 2019; Wodtke and Zhou 2019). The rwrmed() function fits user-specified mediator and outcome models with residualized post-treatment confounders. The decomp() function implements a two-component...
An R package implementing the stratification index (Zhou 2012). The package provides two functions, srank(), which returns stratum-specific information, including population share and average percentile rank; and strat(), which returns the stratification index and its approximate standard error. When a grouping factor is specified, strat also provides a detailed decomposition of the overall... Read more about strat: An Implementation of the Stratification Index