Representational Separability Analysis (inter-to-intra scatter ratio)

A Fisher-discriminant-style score S(l,k) = ||mu_A - mu_B|| / (intra-cluster variances) computed per layer/attention-head on a frozen model's real activations, quantifying how entangled or separable two behaviorally-defined classes' representation manifolds are at that specific site — used to rank sites for a targeted geometric intervention rather than intervening uniformly.