Research preview

Yesterday’s earnings releases moved a set of large‑cap stocks – UnitedHealth, JPMorgan, Johnson & Johnson, Goldman Sachs, Wells Fargo, Citigroup, Domino’s, Albertsons and Facebook‑parent Meta – in divergent directions. For systematic traders the pattern of price changes provides a live case study of how noisy short‑term moves can be mistaken for signal, especially when models are built on many predictors relative to limited data. This article walks through the statistical ideas behind over‑fitting, illustrates them with the earnings‑day moves, and offers concrete steps to keep your models robust....