Table V.
Parameter Estimates of the Longitudinal Bidimensional Integrated Item Response Theory Model
| Parameter | Value |
|---|---|
| BaselineV (voiding scale) | − 0.0321 |
| BaselineS (storage scale) | − 0.0347 |
| PmaxV (maximal placebo response voiding scale) | − 0.939 |
| PmaxS (maximal placebo response storage scale) | − 1.36 |
| TprogV (placebo half-life voiding scale) | 12.3 |
| TprogS (placebo half-life storage scale) | 14 |
| Weibull shape parameter (common for both scales) | 1.6 |
| Drug effect voiding scale | − 0.369 |
| Drug effect storage scale | − 0.634 |
| Interindividual variability (IIV) | |
| IIV Baselinev (voiding scale) | 98.6% |
| IIV BaselineS (storage scale) | 128.1% |
| IIV Baselinev-BaselineS correlation | 28.9% |
| IIV Pmax (common for both scales) | 114.9% |
| IIV Tprog (common for both scales) | 60.8% |
| IIV Drift (common for both scales) | 0.6% |
| IIV Pmax-Drift correlation | 33.2% |
Interindividual variability was assumed normally distributed for the Baseline, Pmax, and Drift parameters and lognormally distributed for the Tprog parameter. No relative standard errors were computed due to model stability issues