{"abstract":"Trimming arrival order does not remove the extremes.","category":"Statistics","checks":4,"contract":"Integer finite observations and equal lengths for paired samples. Counts and weights are nonnegative. Rational results use reduced Fraction strings. Empty or undefined statistics return None where shown. k>=0; sort and remove exactly k values from each tail, returning None if no values remain. Exact operational definition: str(Fraction(sum(sorted(values)[k:len(values)-k]),len(values)-2*k)) if len(values)>2*k else None","contract_signature":"values, k","evaluation_group":"model-16d19ea6dc309389","failed_approach":"Only the lower tail is trimmed.","family":"xn-trimmed-mean-drop-each-tail","id":"FA-6226","implementations":{"attempt":{"sha256":"1a30dd809fa742bb29e66499488911583e2a9130ce537bf2bf8a418a72e446db","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(values, k):\n    return str(Fraction(sum(sorted(values)[k:]),len(values)-k)) if len(values)>k else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: ([100, 1, 2, 3, 4], 1)', solve(*([100, 1, 2, 3, 4], 1)), '3')\ncheck('fixture 2: ([1, 2, 3], 0)', solve(*([1, 2, 3], 0)), '2')\ncheck('fixture 3: ([1, 2], 1)', solve(*([1, 2], 1)), None)\ncheck('fixture 4: ([5, 5, 5, 5], 1)', solve(*([5, 5, 5, 5], 1)), '5')\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"25cb287b5ffd7f7c0c4ff4b26b3444d370cd084533ced25bae52a1a7d4f06583","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(values, k):\n    return str(Fraction(sum(values[k:len(values)-k]),len(values)-2*k)) if len(values)>2*k else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: ([100, 1, 2, 3, 4], 1)', solve(*([100, 1, 2, 3, 4], 1)), '3')\ncheck('fixture 2: ([1, 2, 3], 0)', solve(*([1, 2, 3], 0)), '2')\ncheck('fixture 3: ([1, 2], 1)', solve(*([1, 2], 1)), None)\ncheck('fixture 4: ([5, 5, 5, 5], 1)', solve(*([5, 5, 5, 5], 1)), '5')\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xn-trimmed-mean-drop-each-tail","generated_at":"2026-09-29T14:37:59.065172+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Small exact fixtures expose this error without platform timing, external services, or probabilistic observations. Statistical estimators results depend on the stated convention.","root_cause":"Trimming arrival order does not remove the extremes.","sha256":"ef4bb3060fc67dc950a66623f8fb96edd3838ee3d7c389ede4c317ad3c06aa65","title":"Trimmed mean drop each tail · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":50.174,"exit_code":1,"observations":[{"actual":"109/4","check":"fixture 1: ([100, 1, 2, 3, 4], 1)","expected":"3","passed":false},{"actual":"2","check":"fixture 2: ([1, 2, 3], 0)","expected":"2","passed":true},{"actual":"2","check":"fixture 3: ([1, 2], 1)","expected":null,"passed":false},{"actual":"5","check":"fixture 4: ([5, 5, 5, 5], 1)","expected":"5","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ([100, 1, 2, 3, 4], 1)\", \"actual\": \"109/4\", \"expected\": \"3\", \"passed\": false}, {\"check\": \"fixture 2: ([1, 2, 3], 0)\", \"actual\": \"2\", \"expected\": \"2\", \"passed\": true}, {\"check\": \"fixture 3: ([1, 2], 1)\", \"actual\": \"2\", \"expected\": null, \"passed\": false}, {\"check\": \"fixture 4: ([5, 5, 5, 5], 1)\", \"actual\": \"5\", \"expected\": \"5\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":43.198,"exit_code":1,"observations":[{"actual":"2","check":"fixture 1: ([100, 1, 2, 3, 4], 1)","expected":"3","passed":false},{"actual":"2","check":"fixture 2: ([1, 2, 3], 0)","expected":"2","passed":true},{"actual":null,"check":"fixture 3: ([1, 2], 1)","expected":null,"passed":true},{"actual":"5","check":"fixture 4: ([5, 5, 5, 5], 1)","expected":"5","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ([100, 1, 2, 3, 4], 1)\", \"actual\": \"2\", \"expected\": \"3\", \"passed\": false}, {\"check\": \"fixture 2: ([1, 2, 3], 0)\", \"actual\": \"2\", \"expected\": \"2\", \"passed\": true}, {\"check\": \"fixture 3: ([1, 2], 1)\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"fixture 4: ([5, 5, 5, 5], 1)\", \"actual\": \"5\", \"expected\": \"5\", \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}