Answer:
Formal research methods 
Step-by-step explanation:
Formal research methods - 
It refers to the research method , which uses the basic and traditional search sources and experiments , is referred to as formal research methods . 
In this research method , the sample used is a random sample . 
The research method involve the use of library as the source of information and some experiments to conduct the research . 
Hence , from the given information of the question , 
The correct term is Formal research methods .