Artemis surface stress test -- hypothesis tests
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H1 -- pre-fix failure clustering (Wald-Wolfowitz runs test)
  H0: pass/fail outcomes are independently ordered (no clustering).
  Observed runs = 26 (expected under H0 = 26.00, sd = 3.50)
  z = 0.000, p = 1.00e+00
  -> fail to reject H0 at alpha=0.05: failures are not serially clustered.

H1b -- pre-fix outcome vs. trial/write order directly (Wilcoxon)
  H0: trial index is drawn from the same distribution for PASS/FAIL
      (complements H1: the runs test only catches consecutive-value
      clustering, not a general rank-order trend).
  W = 332.0, p = 0.715
  -> fail to reject H0 at alpha=0.05: outcome is not associated with write order.

H2 -- pre-fix failure vs. disk location (Wilcoxon rank-sum test)
  H0: logical block number is drawn from the same distribution
      for PASS and FAIL trials (failure does not depend on location).
  W = 505.0, p = 0.000
  -> REJECT H0 at alpha=0.05: failure IS associated with LBN.

  Secondary check -- sibling position (0/1/2) vs. outcome (chi-squared)
  chi-sq = 0.790, df = 2, p = 0.674
  -> fail to reject H0: outcome is not associated with sibling position.

H3 -- did the fix change the pass rate (two-proportion test)
  H0: pre-fix and post-fix trials share the same true pass rate.
  Pre-fix: 25/50 = 50.0%   Post-fix (pooled, 3 arches): 150/150 = 100.0%
  chi-sq = 81.20, df = 1, p = 2.04e-19
  95% CI on the difference in pass rate: [-0.652, -0.348]
  -> REJECT H0 at alpha=0.05: the fix DID CHANGE the pass rate.