Anderson–Darling test 2026-10-14
The test rejects for large values of this tail-weighted empirical discrepancy. For a specified continuous null, its standard limiting statistic is , using a Brownian bridge. The reciprocal variance weight gives tail deviations more influence than the Cramér–von Mises criterion. If null parameters are estimated, fitting must be included when computing or simulating its reference law.
Past exam of the mathematics course of the University of Cambridge 2005 iii Paper 42 6 vii Solution Created 2026-10-03 Updated 2026-10-14
For a fully specified continuous null distribution , compare the empirical distribution function with . The probability integral transform makes iid uniform under the null, giving distribution-free calibration. Three common discrepancies areThese define the Kolmogorov-Smirnov test, Cramér–von Mises criterion and Anderson–Darling test, respectively. Reject for large values. The supremum detects the largest discrepancy, the unweighted integral combines discrepancies throughout the distribution, and the reciprocal weight emphasizes the tails.
The Donsker theorem for empirical distribution functions gives for a Brownian bridge , with covariance . Consequently the standard continuous-null limits are , , and for , respectively; the weighted last limit also requires control near the endpoints. Exact finite-sample or asymptotic null quantiles provide critical values.
If parameters in are estimated from the same observations, these fully specified-null critical values generally fail. A first-order expansion isso the estimated parameter changes the limiting process. One must use the fitted-model null law, adjusted asymptotic theory, or a parametric bootstrap that re-estimates the parameters in each replicate.