2sigma Two standard deviations, at scale.

On Bloom’s Two Sigma Problem.

Fig. 1 — Bloom (1984) μ₁ = 0σ  ·  μ₂ = +2σ
The two-sigma effect — one-on-one tutoring shifts the distribution two standard deviations to the right.

In 1984, Benjamin Bloom showed that students tutored one-on-one performed two standard deviations above peers taught in a conventional classroom. Forty years on, closing that gap at scale remains education’s open problem. I’m working on it — this time, with AI.

Xinyu Yang
Xinyu Yang
杨新宇 · 2sigma.cc