Grounded theory

Is that a test question? If it is, you'll have to go back to your notes and your textbook for the answer that your teacher wants.

In reality ... grounded theory is one of more common approaches in qualitative research, but there are others that are also quite common. Simple qualitative descriptive designs are common as are phenomenologic studies and ethnographies. Different methods have been popular in different years/decades.

To get the "perfect" answer to your question, someone would have to collect all the published studies and tally up the methods used. I don't think anybody has done that. So ... if you are trying to answer that question to satisfy an instructor, you'll have to look at the references he/she is using and answer the question based on that person's opinion.

Your choice of a methodology should match your research question. You should not choose your methodology based on "what's the most common" or anything like that.

Nurses use a variety of methods for qualitative research -- and you should familiarize yourself with most of the major ones before you choose one to do a study. For example:

For grounded theory, the underlying question is, "What is the basic social process that explains ...?"

For ethnography, the underlying question is, "What is the culture that ...?"

For phenomenology, the underlying question is, "What is it like ...?" or "What is the lived experience of ...?"

For a qualitative descriptive study, the underlying question is a more general, "What are the key features of ...?" or "How would you describe ...?"

First, become thoroughly familiar with the research that has already done on your topic of interest. Based on that review, decide what question needs to be answered. Then choose the method that is designed to answer that question.

If you are unfamiliar/inexperienced in the conduct of qualitative research, you should have an advisor or mentor helping you through the process. Not only can such a person help you choose a question and a method, but he/she can help you with the necessary paperwork for the IRB, etc.

Good luck!