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Quantitative Finance · Glosario

¿Qué es Population stability index?

Definition 27.2 Machine Learning for Markets · Capítulo 27 — Monitoring and Retraining

Cut a reference sample of a variable into BB bins (here its deciles) with shares r1,…,rBr_1,\dots,r_B, and let q1,…,qBq_1,\dots,q_B be the shares of a new sample in the same bins. The population stability index is

PSI=∑b=1B(qb−rb)ln⁡qbrb,\mathrm{PSI}=\sum_{b=1}^{B}(q_b-r_b)\ln\frac{q_b}{r_b},

the symmetrised Kullback–Leibler divergence between the two binned distributions (empty bins are floored at a small share).

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