Research7 min read
Vector Scores Are Not Probabilities: Likelihood Ratio Calibration for Hybrid Search
by Jaepil Jeong | March 25, 2026
A cosine similarity of 0.85 tells you an angle, not a probability. We show how to transform vector similarity scores into calibrated relevance probabilities using distributional statistics that ANN indexes already compute — completing the probabilistic unification of text and vector retrieval.