Right. Another way of saying it is there isn't random assignment of the subjects to the two conditions in the study.

换种方式说,受试者并不是随机安排在,这个研究中的两种情况下。

耶鲁公开课 - 心理学导论课程节选

OCW Self learners are coming to OCW to explore whole new areas of study as well as to brush up on subjects that they took a while ago and perhaps got the rest in the end.

自学者浏览,搜索全新领域的研究,补充学过的科目的知识,使之完整。

麻省理工公开课 - 媒体、教育、市场课程节选

But you can imagine the inability to do that in a big population study with thousands and thousands of subjects, so we have to rely on data like this.

但你们可以想象在一个大样本研究中,不可能对数以千计的研究对象做这种培训,所以我们需要依靠像这样的数据

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

This study is very interesting because what it did was take nurses, a cohort of a hundred thousand nurses -my wife is actually--just happens to be one of the subjects in this study because she's a nurse.

这项研究很有趣,它将十万名护士作为实验对象,我的太太恰好也是其中一名实验对象,她也是一名护士

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选