医学的最大进展之一，是20世纪50 年代中期采用的一种新研究技术，叫做“临床对照试验”，用来确定新药和其他治疗是否安全有效。

One of the greatest advances in medicine was the introduction of a new research technique in the mid-1950s called the controlled clinical trial, which is used to determine if new drugs and other treatments are safe and effective. 

在临床对照试验中，一组病人，即治疗组，接受新药或新的疗法。另一组病人，即对照组，服用无药性的丸剂（安慰剂），或接受标准的治疗。

In the controlled clinical trial, one group of patients, the treatment group, receives the new drug or new treatment. Another group, the control group, is given an inactive pill (a placebo) or the best standard treatment. 

研究人员然后对经过一个时期治疗的两组病人作比较，用严格的统计技术对收集的数据做分析，以确定新的疗法是否比标准疗法或不治疗更安全有效。

Researchers then compare the two groups after a period of treatment and analyze the data collected  through rigorous statistical techniques to determine whether the new treatment is safer and more effective than standard therapy or no treatment.

多数临床试验在单盲或双盲基础上进行。在单盲试验中，病人不知道他们接受的是新药还是安慰剂。在双盲试验中，病人和医生都不知道哪位病人在接受新的治疗。

Most clinical trials are conducted on a blind or double-blind basis. In a blind trial, patients do not know whether they receive the new drug or a placebo. In a double-blind trial, neither patients nor physicians know who is receiving the new treatment. 

这一保密是重要的，因为病人如果知道自己在用一种强力的新药，会期望感到病情好转，并向医生报告。

This secrecy is important because patients who know they are taking a powerful new drug may expect to feel better and report improvement to doctors. 

研究人员如果知道一个病人在接受试验的新疗法，也可能会看到病人情况改善，而实际上并无改善。

Researchers who know that a patient is receiving the test treatment may also see improvements that really do not exist.

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