{
  "dataset": {
    "name_zh": "NTJ 日語學習作答彙總資料集 2026 年 10 月",
    "name_en": "NTJ Japanese Learning Answer Dataset — October 2026",
    "version": "2.0.0",
    "methodology_version": "2.0",
    "snapshot_date": "2026-10-21",
    "generated_at_utc": "2026-10-23T00:00:00Z",
    "temporal_coverage": "2026-08-02/2026-10-21",
    "publisher": "Nihongo to Japan",
    "url": "https://www.nihongotojapan.com/research/japanese-learning-data-2026-10",
    "previous_version_url": "https://www.nihongotojapan.com/research/japanese-learning-data-2026",
    "license_status": "CC-BY-4.0",
    "source": "public aggregate endpoints /api/aggregates (kind=summary, items, difficulty, spacing, brier) and /api/community (kind=overview)",
    "source_snapshot_at_utc": {
      "summary": "2026-10-21T19:18:19.050Z",
      "items": "2026-10-21T19:20:27.900Z",
      "difficulty": "2026-10-21T19:18:02.883Z",
      "spacing": "2026-10-18T19:47:27.768Z",
      "brier": "2026-10-21T19:19:14.382Z"
    },
    "input_sha256": {
      "aggregates_kind_summary.json": "89351b66359feec1758147bbbc09850a4e543d009d7c455a76742af49bbe94a6",
      "items.json": "97438887cdbda852cb5f26c8822b793b28f5963352c0ecd56b91c66c8869446c",
      "diff.json": "266c1cc9b0fc07c34c1fc2b9593175be8aa3b979cf30e76e7d73d6ee4659dcba",
      "spacing.json": "f8e3d0f0890950b42fb3f8df3d175843d44b8c76913d3e3434fc50bbabf3cbd7",
      "brier.json": "acfe09a2b1af7885bdb07695515ac2028592b224052330438559edfffd7aae25",
      "community_kind_overview.json": "54a891fba7159f8b80bf3ac55ae238faab3e8e8cff1bf03c3d340af9eb32d8af"
    }
  },
  "license": {
    "status": "CC-BY-4.0",
    "spdx": "CC-BY-4.0",
    "url": "https://creativecommons.org/licenses/by/4.0/",
    "attribution_zh": "Nihongo to Japan,《日語學習作答彙總資料集・2026 年 10 月》v2.0.0, CC BY 4.0, https://www.nihongotojapan.com/research/japanese-learning-data-2026-10",
    "attribution_en": "Nihongo to Japan, Japanese Learning Answer Dataset — October 2026, v2.0.0, CC BY 4.0, https://www.nihongotojapan.com/research/japanese-learning-data-2026-10",
    "scope_note_en": "CC BY 4.0 covers the data only (the figures and the JSON/CSV files). Charts and report text are not covered."
  },
  "totals": {
    "valid_answer_events": 543344,
    "learner_identifiers_grade_a": 5410,
    "learner_identifiers_all": 8073,
    "live_counter_events_at_freeze": 552850,
    "distinct_questions": 25850,
    "items_in_item_analysis": 7057,
    "items_with_adjusted_difficulty": 18139,
    "days_covered": 81,
    "knowledge_points_reported": 100,
    "evidence_class_ratio": {
      "A": 0.598,
      "B": 0.335,
      "C": 0.067
    },
    "spaced_review_events": 37314,
    "growth_vs_v1": 9.6
  },
  "thresholds": {
    "min_n_to_report": 300,
    "min_item_exposure": 20,
    "note_en": "Event-level cells with n<300 are suppressed; item-level analyses use questions with >=20 exposures."
  },
  "by_axis_all_events": [
    {
      "key": "vocab",
      "n": 267127,
      "correct_pct": 90.1,
      "naive_ci95": [
        90.0,
        90.2
      ],
      "reported": true
    },
    {
      "key": "pattern",
      "n": 234602,
      "correct_pct": 75.2,
      "naive_ci95": [
        75.1,
        75.4
      ],
      "reported": true
    },
    {
      "key": "wordform",
      "n": 18479,
      "correct_pct": 75.2,
      "naive_ci95": [
        74.5,
        75.8
      ],
      "reported": true
    },
    {
      "key": "particle",
      "n": 13870,
      "correct_pct": 71.3,
      "naive_ci95": [
        70.6,
        72.1
      ],
      "reported": true
    },
    {
      "key": "idiom",
      "n": 7413,
      "correct_pct": 88.1,
      "naive_ci95": [
        87.4,
        88.8
      ],
      "reported": true
    },
    {
      "key": "reading",
      "n": 1103,
      "correct_pct": 78.7,
      "naive_ci95": [
        76.2,
        81.0
      ],
      "reported": true
    },
    {
      "key": "listening",
      "n": 605,
      "correct_pct": 69.8,
      "naive_ci95": [
        66.0,
        73.3
      ],
      "reported": true
    },
    {
      "key": "speaking",
      "n": 118,
      "correct_pct": null,
      "naive_ci95": null,
      "reported": false
    },
    {
      "key": "allround",
      "n": 27,
      "correct_pct": null,
      "naive_ci95": null,
      "reported": false
    }
  ],
  "by_jlpt_all_events": [
    {
      "key": "N5",
      "n": 297809,
      "correct_pct": 87.1,
      "naive_ci95": [
        86.9,
        87.2
      ],
      "reported": true
    },
    {
      "key": "N4",
      "n": 93609,
      "correct_pct": 79.5,
      "naive_ci95": [
        79.3,
        79.8
      ],
      "reported": true
    },
    {
      "key": "N3",
      "n": 82010,
      "correct_pct": 75.3,
      "naive_ci95": [
        75.0,
        75.6
      ],
      "reported": true
    },
    {
      "key": "N2",
      "n": 36837,
      "correct_pct": 74.8,
      "naive_ci95": [
        74.4,
        75.3
      ],
      "reported": true
    },
    {
      "key": "N1",
      "n": 33082,
      "correct_pct": 78.1,
      "naive_ci95": [
        77.7,
        78.5
      ],
      "reported": true
    }
  ],
  "item_level_by_jlpt": [
    {
      "key": "N5",
      "items": 3817,
      "items_with_adjusted": 2540,
      "first_attempt_pct": 82.6,
      "first_attempt_ci95": [
        82.1,
        83.2
      ],
      "adjusted_error_pct": 22.0,
      "adjusted_error_ci95": [
        21.3,
        22.7
      ]
    },
    {
      "key": "N4",
      "items": 1766,
      "items_with_adjusted": 1341,
      "first_attempt_pct": 84.5,
      "first_attempt_ci95": [
        83.6,
        85.3
      ],
      "adjusted_error_pct": 20.6,
      "adjusted_error_ci95": [
        19.8,
        21.4
      ]
    },
    {
      "key": "N3",
      "items": 1008,
      "items_with_adjusted": 847,
      "first_attempt_pct": 75.7,
      "first_attempt_ci95": [
        74.3,
        77.0
      ],
      "adjusted_error_pct": 24.7,
      "adjusted_error_ci95": [
        23.7,
        25.8
      ]
    },
    {
      "key": "N2",
      "items": 249,
      "items_with_adjusted": 204,
      "first_attempt_pct": 66.9,
      "first_attempt_ci95": [
        64.0,
        69.8
      ],
      "adjusted_error_pct": 28.8,
      "adjusted_error_ci95": [
        26.1,
        31.6
      ]
    },
    {
      "key": "N1",
      "items": 217,
      "items_with_adjusted": 210,
      "first_attempt_pct": 74.2,
      "first_attempt_ci95": [
        71.0,
        77.4
      ],
      "adjusted_error_pct": 26.7,
      "adjusted_error_ci95": [
        23.7,
        29.8
      ]
    }
  ],
  "item_level_by_axis": [
    {
      "key": "vocab",
      "items": 3398,
      "items_with_adjusted": 3398,
      "first_attempt_pct": 89.1,
      "first_attempt_ci95": [
        88.7,
        89.5
      ],
      "adjusted_error_pct": 16.4,
      "adjusted_error_ci95": [
        16.0,
        16.8
      ]
    },
    {
      "key": "pattern",
      "items": 3252,
      "items_with_adjusted": 1475,
      "first_attempt_pct": 73.9,
      "first_attempt_ci95": [
        73.1,
        74.7
      ],
      "adjusted_error_pct": 37.4,
      "adjusted_error_ci95": [
        36.5,
        38.3
      ]
    },
    {
      "key": "wordform",
      "items": 154,
      "items_with_adjusted": 70,
      "first_attempt_pct": 76.2,
      "first_attempt_ci95": [
        73.5,
        78.9
      ],
      "adjusted_error_pct": 14.0,
      "adjusted_error_ci95": [
        10.9,
        17.0
      ]
    },
    {
      "key": "particle",
      "items": 189,
      "items_with_adjusted": 135,
      "first_attempt_pct": 67.6,
      "first_attempt_ci95": [
        64.9,
        70.4
      ],
      "adjusted_error_pct": 26.8,
      "adjusted_error_ci95": [
        24.4,
        29.2
      ]
    },
    {
      "key": "idiom",
      "items": 64,
      "items_with_adjusted": 64,
      "first_attempt_pct": 92.4,
      "first_attempt_ci95": [
        90.8,
        93.9
      ],
      "adjusted_error_pct": 7.0,
      "adjusted_error_ci95": [
        5.7,
        8.2
      ]
    }
  ],
  "item_first_attempt_distribution": [
    {
      "from_pct": 0,
      "to_pct": 35,
      "items": 283
    },
    {
      "from_pct": 35,
      "to_pct": 50,
      "items": 377
    },
    {
      "from_pct": 50,
      "to_pct": 70,
      "items": 971
    },
    {
      "from_pct": 70,
      "to_pct": 85,
      "items": 1347
    },
    {
      "from_pct": 85,
      "to_pct": 95,
      "items": 1937
    },
    {
      "from_pct": 95,
      "to_pct": 100,
      "items": 2142
    }
  ],
  "item_quality": {
    "items": 7057,
    "first_attempt_below_35": 283,
    "first_attempt_below_35_pct": 4.0,
    "flagged_for_review": 415
  },
  "particles_all_events": [
    {
      "key": "kp_particle_で",
      "label": "で",
      "n": 1741,
      "correct_pct": 62.6,
      "naive_ci95": [
        60.3,
        64.8
      ]
    },
    {
      "key": "kp_particle_が",
      "label": "が",
      "n": 2251,
      "correct_pct": 63.0,
      "naive_ci95": [
        61.0,
        65.0
      ]
    },
    {
      "key": "kp_particle_に",
      "label": "に",
      "n": 1948,
      "correct_pct": 64.7,
      "naive_ci95": [
        62.5,
        66.8
      ]
    },
    {
      "key": "kp_particle_と",
      "label": "と",
      "n": 526,
      "correct_pct": 74.3,
      "naive_ci95": [
        70.4,
        77.9
      ]
    },
    {
      "key": "kp_particle_を",
      "label": "を",
      "n": 1684,
      "correct_pct": 80.6,
      "naive_ci95": [
        78.6,
        82.4
      ]
    },
    {
      "key": "kp_particle_の",
      "label": "の",
      "n": 467,
      "correct_pct": 85.2,
      "naive_ci95": [
        81.7,
        88.2
      ]
    }
  ],
  "patterns_all_events": [
    {
      "key": "kp_pattern_らしい",
      "label": "らしい",
      "n": 855,
      "correct_pct": 46.5,
      "naive_ci95": [
        43.2,
        49.9
      ]
    },
    {
      "key": "kp_pattern_はず",
      "label": "はず",
      "n": 592,
      "correct_pct": 53.4,
      "naive_ci95": [
        49.4,
        57.4
      ]
    },
    {
      "key": "kp_pattern_ように",
      "label": "ように",
      "n": 807,
      "correct_pct": 54.2,
      "naive_ci95": [
        50.7,
        57.6
      ]
    },
    {
      "key": "kp_pattern_うえに",
      "label": "うえに",
      "n": 471,
      "correct_pct": 55.2,
      "naive_ci95": [
        50.7,
        59.6
      ]
    },
    {
      "key": "kp_pattern_ながら",
      "label": "ながら",
      "n": 974,
      "correct_pct": 58.0,
      "naive_ci95": [
        54.9,
        61.1
      ]
    },
    {
      "key": "kp_pattern_てから",
      "label": "てから",
      "n": 776,
      "correct_pct": 60.7,
      "naive_ci95": [
        57.2,
        64.1
      ]
    },
    {
      "key": "kp_pattern_において",
      "label": "において",
      "n": 483,
      "correct_pct": 60.9,
      "naive_ci95": [
        56.4,
        65.1
      ]
    },
    {
      "key": "kp_pattern_たら",
      "label": "たら",
      "n": 1084,
      "correct_pct": 64.4,
      "naive_ci95": [
        61.5,
        67.2
      ]
    },
    {
      "key": "kp_pattern_くて",
      "label": "くて",
      "n": 518,
      "correct_pct": 65.4,
      "naive_ci95": [
        61.2,
        69.4
      ]
    },
    {
      "key": "kp_pattern_て",
      "label": "て",
      "n": 3618,
      "correct_pct": 66.2,
      "naive_ci95": [
        64.6,
        67.7
      ]
    },
    {
      "key": "kp_pattern_わけ",
      "label": "わけ",
      "n": 811,
      "correct_pct": 66.2,
      "naive_ci95": [
        62.9,
        69.4
      ]
    },
    {
      "key": "kp_pattern_ても",
      "label": "ても",
      "n": 1416,
      "correct_pct": 68.1,
      "naive_ci95": [
        65.7,
        70.5
      ]
    },
    {
      "key": "kp_pattern_にとって",
      "label": "にとって",
      "n": 479,
      "correct_pct": 70.6,
      "naive_ci95": [
        66.3,
        74.5
      ]
    },
    {
      "key": "kp_pattern_かもしれない",
      "label": "かもしれない",
      "n": 487,
      "correct_pct": 71.9,
      "naive_ci95": [
        67.7,
        75.7
      ]
    },
    {
      "key": "kp_pattern_にもかかわらず",
      "label": "にもかかわらず",
      "n": 538,
      "correct_pct": 72.7,
      "naive_ci95": [
        68.8,
        76.3
      ]
    },
    {
      "key": "kp_pattern_によって",
      "label": "によって",
      "n": 595,
      "correct_pct": 76.8,
      "naive_ci95": [
        73.2,
        80.0
      ]
    },
    {
      "key": "kp_pattern_てしまった",
      "label": "てしまった",
      "n": 494,
      "correct_pct": 78.3,
      "naive_ci95": [
        74.5,
        81.7
      ]
    },
    {
      "key": "kp_pattern_すぎ",
      "label": "すぎ",
      "n": 556,
      "correct_pct": 78.6,
      "naive_ci95": [
        75.0,
        81.8
      ]
    },
    {
      "key": "kp_pattern_そう",
      "label": "そう",
      "n": 795,
      "correct_pct": 82.4,
      "naive_ci95": [
        79.6,
        84.9
      ]
    },
    {
      "key": "kp_pattern_こと",
      "label": "こと",
      "n": 2669,
      "correct_pct": 84.1,
      "naive_ci95": [
        82.7,
        85.5
      ]
    },
    {
      "key": "kp_pattern_よう",
      "label": "よう",
      "n": 1698,
      "correct_pct": 84.5,
      "naive_ci95": [
        82.7,
        86.2
      ]
    },
    {
      "key": "kp_pattern_に対して",
      "label": "に対して",
      "n": 893,
      "correct_pct": 85.8,
      "naive_ci95": [
        83.3,
        87.9
      ]
    },
    {
      "key": "kp_pattern_まま",
      "label": "まま",
      "n": 1146,
      "correct_pct": 92.3,
      "naive_ci95": [
        90.6,
        93.7
      ]
    },
    {
      "key": "kp_pattern_なければなりません",
      "label": "なければなりません",
      "n": 988,
      "correct_pct": 93.1,
      "naive_ci95": [
        91.4,
        94.5
      ]
    }
  ],
  "conjugations_all_events": [
    {
      "key": "kp_conj_potential",
      "label": "可能形 potential",
      "n": 1923,
      "correct_pct": 64.5,
      "naive_ci95": [
        62.3,
        66.6
      ]
    },
    {
      "key": "kp_conj_ta",
      "label": "た形 ta-form",
      "n": 2704,
      "correct_pct": 70.7,
      "naive_ci95": [
        69.0,
        72.4
      ]
    },
    {
      "key": "kp_conj_te",
      "label": "て形 te-form",
      "n": 3061,
      "correct_pct": 74.1,
      "naive_ci95": [
        72.5,
        75.6
      ]
    },
    {
      "key": "kp_conj_nai",
      "label": "ない形 nai-form",
      "n": 2862,
      "correct_pct": 75.0,
      "naive_ci95": [
        73.4,
        76.5
      ]
    },
    {
      "key": "kp_conj_masu",
      "label": "ます形 masu-form",
      "n": 2270,
      "correct_pct": 84.0,
      "naive_ci95": [
        82.4,
        85.5
      ]
    }
  ],
  "spacing": [
    {
      "bucket": "0_lt_1h",
      "label_zh": "< 1 小時",
      "label_en": "< 1 hour",
      "n": 172323,
      "learner_identifiers": 3472,
      "correct_pct": 84.1,
      "naive_ci95": [
        84.0,
        84.3
      ],
      "avg_gap_hours": 0.0
    },
    {
      "bucket": "1_1h_1d",
      "label_zh": "1 小時–1 天",
      "label_en": "1 hour – 1 day",
      "n": 5749,
      "learner_identifiers": 647,
      "correct_pct": 76.7,
      "naive_ci95": [
        75.6,
        77.8
      ],
      "avg_gap_hours": 10.3
    },
    {
      "bucket": "2_1d_3d",
      "label_zh": "1–3 天",
      "label_en": "1–3 days",
      "n": 11714,
      "learner_identifiers": 532,
      "correct_pct": 87.3,
      "naive_ci95": [
        86.7,
        87.9
      ],
      "avg_gap_hours": 45.4
    },
    {
      "bucket": "3_3d_7d",
      "label_zh": "3–7 天",
      "label_en": "3–7 days",
      "n": 11864,
      "learner_identifiers": 449,
      "correct_pct": 87.4,
      "naive_ci95": [
        86.8,
        88.0
      ],
      "avg_gap_hours": 114.6
    },
    {
      "bucket": "4_7d_30d",
      "label_zh": "7–30 天",
      "label_en": "7–30 days",
      "n": 13007,
      "learner_identifiers": 405,
      "correct_pct": 87.0,
      "naive_ci95": [
        86.4,
        87.6
      ],
      "avg_gap_hours": 324.6
    },
    {
      "bucket": "5_gt_30d",
      "label_zh": "> 30 天",
      "label_en": "> 30 days",
      "n": 729,
      "learner_identifiers": 126,
      "correct_pct": 79.3,
      "naive_ci95": [
        76.2,
        82.1
      ],
      "avg_gap_hours": 904.2
    }
  ],
  "prediction_brier": {
    "n": 257010,
    "learner_identifiers": 4315,
    "actual_correct_pct": 79.9,
    "v1_brier": 0.4089,
    "v2_brier": 0.1987,
    "v2_item_brier": 0.1304,
    "improvement_pct": 51.4,
    "item_improvement_pct": 68.1,
    "baseline_constant_brier": 0.1605
  }
}