https://github.com/python/cpython/commit/41f0b78cbf204649bbae71662a115425c58f048d commit: 41f0b78cbf204649bbae71662a115425c58f048d branch: master author: Raymond Hettinger <rhettinger at users.noreply.github.com> committer: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com> date: 2019年03月14日T02:25:26-07:00 summary: Simplify overlap() formula for case where variances are equal (GH-12323) files: M Lib/statistics.py diff --git a/Lib/statistics.py b/Lib/statistics.py index 97f154373dc0..8d79eed6b1aa 100644 --- a/Lib/statistics.py +++ b/Lib/statistics.py @@ -773,7 +773,7 @@ def overlap(self, other): dv = Y_var - X_var dm = fabs(Y.mu - X.mu) if not dv: - return 2.0 * NormalDist(dm, 2.0 * X.sigma).cdf(0) + return 1.0 - erf(dm / (2.0 * X.sigma * sqrt(2.0))) a = X.mu * Y_var - Y.mu * X_var b = X.sigma * Y.sigma * sqrt(dm**2.0 + dv * log(Y_var / X_var)) x1 = (a + b) / dv