Research proposal is the all
For any reason, there should be the path to reach the conclusion that one should research. Before the research, one should have the quenstion which can be derived from anything such that the persuit of personal interest or the hope to contribute to humankinds. Then one will search and aquire the knowledge for the existent results about the question of interest. If one could have the complete answer for the question, that is all. If not, one can be motivated for the research with the question of interest.
Then, actually, the potential of applicants for Ph.D. programmes should be guess for the research proposals of them. Theoretically all of the people who hope to research seriously should have done the "research" about the existent results which can be noted in the proposal. Through the "research", they could have obtained the ordinary methodological knowledge about the relevant topics and how they can implement the research in time series. Without any entrance exam, the department and the professors can distinguish the good apples and the bad ones with the proposal since they are the expert. Hence, ideally, the research proposal should be only the requirement for the application to Ph.D. programmes. Realistically speaking, the other materials such that the letters of recommendations and GRE are necessary as the support for the decision.
The distance between basic research and applied research
There is the unignorable distance between basic research and applied one: researchers in basic research cannot mean that they can do applied research and vice versa.
To cross those fields, it is significant to recognise the difference in motivation. The applied research utilises the best method to solve the specific problem and the applied researchers are problem-solvers or problem-driven researchers in that meaning. With respect to the basic research, the researchers are intersted in theoretical advancement in the specific academic discipline and then they are the theory-driven researchers.
Hence sometimes the research without the comprehension for it triggers problem. The theory-driven researcher hope to verify the validity of the theory in real problem solving and that is the natural motivation. But there is the danger to apply the theory to the problem that should be applied the different best theory because they really do not hope to solve the problem but to generate the value of the theory they made. The applied researchers are required to have the broad theoretical knowledge and the ability to generate the new tailor-made theory for the problem solving.
It is a liuttle bit analogous to that mathematicians are not necessariliy able to do the research in physics.