For a couple of reasons. In some ways, this would be nicer, do expected cases, it's going to tell you on average how much you expect to take, but it tends to be hard to compute, because to compute that, you have to know a distribution on input.

关注最快的情况，在某种意义上来说，因为一些原因这样想挺不错的，当我们处理一个给定的问题,计算平均时间的时候,是很难计算的，因为你并不知道输入的分布情况,这些输入会是怎么样的呢？

麻省理工公开课 - 计算机科学及编程导论课程节选

He speaks in a language of math and it is very important for students to be able to have hot copies so that they can take notes on the paper rather than be working very hard to copy down the equations that he used in these lectures.

他以数学语言授课,所以发给学生教学材料,是非常重要的,这样就可在纸上做笔记,而不用拼命,抄下他在课上,用到的等式。

麻省理工公开课 - 媒体、教育、市场课程节选

And if they're a premade salad then it would be even more difficult because you're not constructing it yourself, so it's hard to uses based on these sort of things.

如果那是预制色拉,就更麻烦了,因为那不是你做的,就很难进行统计

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

Now if all we have to go on is just this semiotic system, it's going to be kind of hard to put up resistance to by the same token we'll say "yellow" means "pause," "green" means "go."

而从语义学角度分析，我们必须不能这么想,这样绿色自然就表示继续，黄色表示暂停“

耶鲁公开课 - 文学理论导论课程节选

When you go into a restaurant now, unless you want to go look at a board on the wall or get a pamphlet that may be hard to find, or go to the website, it's going to be pretty hard to know what you're eating in those foods.

现在当我们去餐馆吃饭时,除非看一看墙上的菜单板,或者是去翻往往很难找到的宣传册,再或者去网站查看,否则很难知道,我们在进餐时到底摄入了些什么成分

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选