What is a focused problem? In my experience, the most difficult things for graduate students to understand are the importance of focusing their research on a single specific problem, how to find that problem, and how specific it should be. Here is a story that might help.
As a birder, I spent many years roaming around in Southeast Arizona with my birding buddy, a retired teacher. Our routine was to spend two weeks camping in various parts of the southeast corner of Arizona. Together, we experienced many of the wonders of the region that included numerous species of birds, accounts of rare or uncommon birds, most of which were really variations in the normal appearance of common species, and many other surprises including a band of 31 coatimundis.
I recall an interesting experience while camping in Cochise Stronghold near Sun Sites, Arizona. We had finished a great day birding and were sitting at the table when I noticed the lanterns at the adjacent campsite. I overheard part of the conversation and realized that it was some kind of field research group. Well, that was enough to make me walk over and introduce myself and inquire about their research. The team was a university professor and his graduate students focused on--get this-- the parasites that lived on ants, not just any ants but select species. I asked how many species of ants were in the area and the answer shocked me. “...probably 100 species, half which have yet to be classified”! One tiny piece of an infinitely large puzzle...
Finding the tiny piece of the puzzle
As you search for a specific problem to address in your graduate work, think about searching for that tiny piece of the grand puzzle of knowledge about your topic. The volumes of previous work about ants and parasites helped the field team find their specific research focus by identifying those areas of the topic that were not clearly explained or understood. In the same way, as you research the literature about your topic area, published scholars will mention those areas they found that need further research and one of those will become your specific research problem. The only way to find the specific problem is to take the time and effort to do a thorough literature review.
Value of an annotated bibliography
One of the best ways to categorize each article you read is to use an annotated bibliography. It is more than an abstract of an article; it is a critical review of the intent, content, and implications of the study. From these annotated bibliographies, you will find recommendations for further research, those questions that arose as the author(s) conducted the study. Reviewing the literature is an ongoing activity throughout your graduate program; older articles will be replaced or supplemented with newer publications. The same applies to the annotated bibliographies as newer sources are found.
Now that you have a focus, go do it!
Once you have thoroughly investigated the literature about your topic, you should be able to easily identify and support a specific problem, build a detailed plan to investigate the problem, implement that plan (do your research), and analyze your findings. Finally, you will give a report of those findings together with your conclusions and recommendations for further research. In this way, your scholarly work--your single piece of the grand puzzle--leads the way for further research by adding to the existing body of knowledge about the topic.