Fig. 3
From: Harmonizing measurements: establishing a common metric via shared items across instruments
Difficulty estimates from model without active equate clusters (ρ = 0.85; γ = 1.94) (left) and model with active equate clusters (ρ = 0.99; γ = -0.03) (right) where difficulty ranges are close, cohort abilities differ and five equate clusters are spread through both instruments. Difficulty estimates are coloured by instrument