题目内容

为观察某草药对致癌物毒性拮抗作用，将60只大鼠随机分三组，每组20只进行毒性实验，对照组发生肿瘤为0只，致癌物组发生肿瘤为15只，草药+致癌物组发生肿瘤为8只。
要比较三组大鼠肿瘤的发生率，问应选用何种统计方法

A. McNemar检验
B. 校正四格表卡方检验
C. 行X列表卡方检验
D. 必须进行合理合并后，再进行卡方检验
E. 只能用Fisher的精确概率法

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