A. because it has no admission fee B. because it is near San Francisco C. because it has a good view of the coast D. because it can be seen in one hour 参考答案:B
第19题: [单项选择]某项关于口腔癌的病因研究中,按照年龄、性别、居住地、社会阶层,对300个口腔癌病人和300个非口腔癌病人逐个配比(非口腔癌病人组中剔除了与吸烟联系密切的疾病),然后调查两组既往的吸烟频率,发现:①病例和对照均吸烟的有96对;②病例和对照均不吸烟的有29对;③病例吸烟而对照不吸烟的有150对;④病例不吸烟而对照吸烟的有25对。该研究的卡方值() A. 87.86 B. 0.97 C. 89.29 D. 0.69 E. 0.74 参考答案:C