实验研究（Experimental Research）
实验研究的目标是要确定两个不同变量之间的因果关系，即一个变量的变化是不是由另一个变量的变化引起的。实验研究一般有两个特征：1.研究者需要变化其中一个变量，也就是自变量（independent variable），来观察另一个变量，也就是因变量（dependent variable）的变化。2.研究者在改变自变量时，需要对实验中的其他无关变量进行控制，确保它们不会影响实验的结果。
The aim of experimental research is to ascertain the causality of two different variables, that is to say, to ascertain whether the changes of one variable is caused by the changes of another one. Experimental research usually have two main features: 1. Researcher need to change one variable(independent variable) in order to observe the changes in another one(dependent variable). 2. The same time changing the independent variables, researchers should also control the irrelevant variables, making sure they won't affect the result of the experiment.
准实验研究（Quasi-experimental Research）
在实验研究之外，还有一种介于实验研究与非实验研究的之间的一种研究，叫做准实验研究（quasi-experimental research）。其对无关变量的控制好于非实验研究，但又不像真实验研究那般严格。在真实的实验中，我们不可能完全控制不同对照组之间的无关变量相等，因此为了获取有用的信息，我们不得不采取折中的办法使用准实验研究。
Beside experimental research, there exists a kind of research between experimental research and non-experimental research, which is called quasi-experimental research. The control of irrelevant variables in this kind of research is superior to non-experimental research, but not as strict as that in experimental research. We may not keep the irrelevant variables all equal in control groups in experimental researches, so we may have to compromise, using quasi-experimental research to obtain useful information.
非实验研究（Non-experimental Research）
最后即为非实验研究，在无关变量的控制上更为不严格的一种研究，一般用于考察自然存在的变量之间的关系。非实验研究能控制的因素更少，相比准实验研究也没有对照组进行比较。
The last kind of research is non-experimental research, whose control of irrelevant variables is way less stricter, and it is usually used for originally existed relationships between variables. Fewer factors could be controlled in non-experimental research, and it doesn't include control groups for comparation, in contrast to quasi-experimental research.