To enter into a PhD program in the United States, students generally must have some form of prerequisite study beyond their basic graduate qualification.
In other countries, entry to Doctoral or Master's research programs is based on the academic track record of the candidates in their undergraduate degrees.
Dario Toncich explains that the objective of postgraduate research is not necessarily to make a breakthrough invention or, indeed, a major scientific discovery.
It is, rather, a mechanism by which graduate students learn how to undertake a systematic investigation, founded upon the work built by peers in the field, and then to extend the current state of knowledge.
[3] In the 19th century, postgraduate research was a rarity, with countries such as the United States only having a small number of candidates across their university spectrum.
There is also some recognition that modern postgraduate research programs now have to be conducted in the light of massive amounts of previously published work, and hence the literature review process has become significantly more complex.
In addition, some universities insist that students also undertake a viva-voce oral examination in which they can defend their research and processes before an expert panel.