And the last thing we do for any of our structures to check them and figure out are these valid or not valid, are these good Lewis structures is to check the formal charge.

而为了检验任何一个结构是否有效,看它们是不是好的路易斯结构,我们要做的最后一件事就是检查形式电荷。

麻省理工公开课 - 化学原理课程节选

What must this experiment have the potential to do, to be a valid scientific experiment?

实验必须有做什么的能力,才能被称为一个有效的科学实验呢？

麻省理工公开课 - 计算机科学及编程导论课程节选

Now, the argument is valid.

现在,这个论证是有效的

耶鲁公开课 - 死亡课程节选

Yes, it's a wonderfully reliable test I'll test you today; I'll test you tomorrow; I'll test you next year; I'll test you the day you die; I'll get the same IQ score ? Is it a valid test?

是的，这是个非常可靠的测试,今天测试，明天再测试;,明年再测，到你死的那天再测;,得出的你的智商都还是一样,但这是个有效测试吗？

耶鲁公开课 - 心理学导论课程节选