Otherwise, statisticians say only strict clinical trials with a control group and a test group and one variable can truly prove a cause-and-effect association.

否则，统计学家表示只有进行严格的临床试验，对比一个控制组、一个测试组以及一个变量，才能真正证明因果关系。

youdao

CONCLUSION: Scientific and strict clinical trials of drugs are helpful to obtain actual and reliable research results.

结论：科学、严谨的药物临床试验设计，有助于获得真实、可靠的研究结果。

youdao

But that is a reason for keeping clinical trials strict.

ECONOMIST: Greens v genes

But such trials typically have strict enrollment criteria and findings often can't be generalized to the broader population.

WSJ: Heart Bypass Surgery May Offer Lower Death Risk Than Angioplasty

The new study, published online in the journal Nature Biotechnology, represents an early example of how social networking could play a role in clinical trials, an area of medical science with strict procedures that many would consider especially difficult to apply in the online world.

WSJ: ALS Study Falls Short, But Use of Social Media Holds Promise