{"abstract":"Absent measurements change the mean even though no observation was recorded.","category":"Numerics","checks":3,"contract":"Use the same set of present observations for both numerator and denominator.","contract_signature":"values","evaluation_group":"model-e942c32c460c4012","failed_approach":"Filtering by truthiness also removes legitimate zero measurements.","family":"missing-values","id":"FA-046","implementations":{"attempt":{"sha256":"5bfd2a3c39f9291f46c18c614f157a9cbe2bd86d2036795f7f8cf2c702acbe3f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(values):\n    present = [x for x in values if x]\n    return sum(present) / len(present) if present else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('missing and zero', solve([None, 0, 2*N]), N)\ncheck('all missing', solve([None, None]), None)\ncheck('no measurements', solve([]), None)\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":"7b773fcc45d5dfc955d7eb3c972a6d5de0acea4f65662967122e78159d745a54","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(values):\n    return sum(x for x in values if x is not None) / len(values) if values else None\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('missing and zero', solve([None, 0, 2*N]), N)\ncheck('all missing', solve([None, None]), None)\ncheck('no measurements', solve([]), None)\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":"missing-values","generated_at":"2026-09-29T14:36:49.880640+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A compact reasoning and repair task with executable evidence.","root_cause":"Missing records remain in the denominator after being removed from the numerator.","sha256":"edff7b0577ad03bab58859224e4b8044b66e1cdaae37dba8b0db97e874ddb491","title":"Missing measurements bias a mean · 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":30.51,"exit_code":1,"observations":[{"actual":2.0,"check":"missing and zero","expected":1,"passed":false},{"actual":null,"check":"all missing","expected":null,"passed":true},{"actual":null,"check":"no measurements","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"missing and zero\", \"actual\": 2.0, \"expected\": 1, \"passed\": false}, {\"check\": \"all missing\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"no measurements\", \"actual\": null, \"expected\": null, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":36.577,"exit_code":1,"observations":[{"actual":0.6666666666666666,"check":"missing and zero","expected":1,"passed":false},{"actual":0.0,"check":"all missing","expected":null,"passed":false},{"actual":null,"check":"no measurements","expected":null,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"missing and zero\", \"actual\": 0.6666666666666666, \"expected\": 1, \"passed\": false}, {\"check\": \"all missing\", \"actual\": 0.0, \"expected\": null, \"passed\": false}, {\"check\": \"no measurements\", \"actual\": null, \"expected\": null, \"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."}}