President Coolidge’s statement, “ The business of America is business” still points to an important truth today—that business institutions have more prestige in American society than any other kind of organization, including the government. Why do business institutions possess this prestige?The statement “ The business of America is business” probably means____.
A. the business institutions in America are concerned with commerce
B. business problems are of great importance to the American government
C. business is of primary concern to Americans
D. America is a great power in world business
查看答案
下列哪项不是流行病学实验设计的原则
A. 设立对照的原则
B. 随机化的原则
C. 重复测量的原则
D. 盲法的原则
下列哪项试验不属于流行病学实验研究
A. 观察性试验
B. 社区试验
C. 现场试验
D. 临床试验
评价人群疫苗接种效果最关键的指标是
A. 安全性
B. 种后反应率
C. 临床表现
D. 保护率
流行病学实验研究中下列哪条不是其缺点
A. 设计严格,实施困难,随访观察花费太大
B. 盲法不易实施,随访时间长,研究人群依从性差
C. 有随机分组很难控制偏倚
D. 易引起医德和伦理学的争议