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Figure 1 | BMC Medical Research Methodology

Figure 1

From: Methodological issues regarding power of classical test theory (CTT) and item response theory (IRT)-based approaches for the comparison of patient-reported outcomes in two groups of patients - a simulation study

Figure 1

Power achieved by the tests of group effects using IRT or CTT. Description: Evolution of the power achieved by the tests of group effects using IRT (Rasch model) or CTT (classical test theory) as a function of the number of items of the questionnaire for an effect size on the latent trait ESIRT = 0.5 and N = 100 patients per group. IRT: item response theory. Situation 2: unknown person parameters and known item parameters; Situation 3: unknown person and item parameters.

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BMC Medical Research Methodology

ISSN: 1471-2288

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