Professor Cheng is teaching an introductory psychology course. Today in class, he is discussing psychology experiments, and he notes that there are two major categories of research design used by psychologists:
descriptive and experimental.

descriptive and experimental

Explanation:

Descriptive research -

It refers to the type of research method , which gives the quality of the process or phenomenon , which is under consideration , is referred to as descriptive research , this study focus on the " what " rather on the " why " factor .

Experimental research -

It refers to the study which sticks to the scientific research design , including , assumptions , hypothesis , theories etc.

Hence , from the given scenario of the question ,

The correct answer is descriptive and experimental .