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Table 3 A priori power estimated with the Raschpower procedure from a pilot study and impact of misspecified parameters on the power ( \(1-\hat {\beta }\) )

From: Power and sample size determination for the group comparison of patient-reported outcomes using the Rasch model: impact of a misspecification of the parameters

Estimations used to determine the power with Raschpower Estimated power Misspecified parameters
Item parameters Group effect Variance of the latent variable \({1-\hat {\beta }}\) Item parameters Variance
Pilot: \(\hat {\delta }_{\textit {jpPILOT}}\) \(\hat {\gamma }_{\textit {PILOT}}=0.1888\) Pilot: \(\hat {\sigma }_{\textit {PILOT}}^{2}=0.7858\) 0.3837 (a priori)   
ELCCA: \(\hat {\delta }_{\textit {jpELCCA}}\) \(\hat {\gamma }_{\textit {PILOT}}=0.1888\) Pilot: \(\hat {\sigma }_{\textit {PILOT}}^{2}=0.7858\) 0.3771 YES  
Pilot: \(\hat {\delta }_{\textit {jpPILOT}}\) \(\hat {\gamma }_{\textit {PILOT}}=0.1888\) ELCCA: \(\hat {\sigma }_{\textit {ELCCA}}^{2}=1.0864\) 0.3004   YES
ELCCA: \(\hat {\delta }_{\textit {jpELCCA}}\) \(\hat {\gamma }_{\textit {PILOT}}=0.1888\) ELCCA: \(\hat {\sigma }_{\textit {ELCCA}}^{2}=1.0864\) 0.2983 YES YES