Mixture IRT: The Safety Valve for Guessing
Interactive companion to XXX (2026)
All plots show performance relative to Oracle — zero is optimal (black line), more negative is worse.
Study 1 · DGP: Mixture · Fitted: Rasch, 1PLg, Mixture, 3PL
0.05 0.5
0.5 0.99
500 5000
10 60
20 80
Orange (1PLg): Applies fixed floor. Crashes away from blue line.
Green (Mixture): Tracks Oracle regardless of g_true.
Purple (3PL): Item-level guessing — modest, variable gain.
Grey (Rasch): Stable but suboptimal baseline.