{
  "id": "S151",
  "type": "单选题",
  "type_code": "single",
  "stem": "样本均值是总体均值的无偏估计的条件是（ ）。",
  "stem_text": "样本均值是总体均值的无偏估计的条件是（ ）。",
  "options": [
    {
      "key": "A",
      "text": "样本容量必须充分大"
    },
    {
      "key": "B",
      "text": "总体必须服从正态分布"
    },
    {
      "key": "C",
      "text": "样本必须是随机抽取的"
    },
    {
      "key": "D",
      "text": "总体方差必须已知"
    }
  ],
  "options_text": [
    {
      "key": "A",
      "text": "样本容量必须充分大"
    },
    {
      "key": "B",
      "text": "总体必须服从正态分布"
    },
    {
      "key": "C",
      "text": "样本必须是随机抽取的"
    },
    {
      "key": "D",
      "text": "总体方差必须已知"
    }
  ],
  "answer_keys": [
    "C"
  ],
  "answer_display": "C",
  "answer_texts": [
    "样本必须是随机抽取的"
  ],
  "sources": [
    {
      "edition": "第14届",
      "edition_num": 14,
      "no": 35,
      "uid": "14-035",
      "file": "第14届市调大赛本科组模拟题(9).docx"
    }
  ],
  "source_display": "第14届 第35题",
  "source_count": 1,
  "images": [],
  "warnings": [],
  "conflict": null,
  "url": "/q/S151.html"
}