We can't know for sure because this is not a controlled experiment.

我们不能确定，因为这不是一个可控实验。

youdao

DESIGN: a controlled experiment was conducted on the basis of clinical diagnosis.

设计：以诊断为依据设立对照的实验研究。

youdao

And in a controlled experiment on hiring decisions, male leaders were not penalized for choosing a woman or nonwhite candidate over an equally qualified white man.

此外，一项关于招聘决策的受控实验显示，男性领导者如果选择了女性或非白人候选人，而非具有同等资历的白人男性，并不会因此受到惩罚。

youdao

Researchers adjusted their computer algorithm to the slower insulin absorption rate and on a repeat experiment blood glucose was tightly controlled in all of the subjects.

VOA: standard.2010.04.15

Whatever the mechanism, though, this study provides what no previous study ever has: evidence from a controlled experiment that keystone species really exist.

ECONOMIST: Ecology: Under the mistletoe | The

Its authors, Steffen Huck and Brian Wallace of University College London (UCL), and Charlotte Duke of London Economics, a consultancy, base that finding on a controlled experiment.

ECONOMIST: Economics focus

Amoruso also tried a controlled experiment.

FORBES: Entrepreneurs