FIGURE 4.

(a) Mean sample size of datasets generated with calculation from pilot trial estimates to have 90% power at a two-sided 5% significance level using the $n_{\text{IPRW}}$, $n_{\text{known}}$, $n_{\text{approx}}$ and $n_{\text{standard}}$ formulas when weighting by a baseline binary covariate in an IRT, where the size of the pilot trial $n_{\text{pilot}}$ is varied on the x-axis. (b) Simulation results displaying the empirical power for each sample size calculation method with the IPRW estimator.