Fig. 5.

Power curves for the unidimensional integrated and the unidimensional International Prostate Symptom Score (IPSS) item response theory pharmacometric models, respectively, using a stochastic simulation and estimation procedure. One thousand simulated data sets from the integrated unidimensional item response theory model at sample sizes of 33, 66, 99, and 137 patients were used for model estimation with the respective full (with a drug effect parameter) and reduced (without a drug effect parameter) models. Vertical lines indicate the 95% confidence interval for the calculated power estimates. A decrease of 3.84 was used to establish significant improvement in objective function between the full and reduced models of the respective approaches