Doctoral research is among the highest level of academic research conducted in universities and institutes throughout the United States. The methods used to conduct Ph.D. research should be sound and the data that results from the research must be credible. Scientific methodologies have been created to ensure the soundness and credibility of doctoral research and to secure continuity in research results. Among the most often employed methodologies are quantitative methods, qualitative methods, comparative methods and clinical trials.

Qualitative Research

Qualitative research methodologies are those scientific approaches that attempt to give meaning to certain experiences by describing cultural phenomena, human behavior or belief systems. Qualitative research is conducted by interviewing people, using a combination of closed and open-ended questions and analyzing the responses to draw conclusions about a pattern of behavior or social phenomena. One example of qualitative research in the field of cognitive learning is obtaining information about students' learning styles by listening to their own subjective descriptions of how they learn.

Quantitative Research

Quantitative research methodology is conducted by collecting data and creating statistics based on the evidence collected to prove or disprove a hypothesis. Quantitative research uses questionnaires or surveys of individuals and compiles the results into a chart, graph or other type of report. Quantitative research is useful in evaluating attitudes or views on certain topics. For example, doctoral research in the field of political science could survey whether people would support a government policy regarding taxes on luxury goods to shed light on the viability of such a proposal in a given community.

Comparative Research

The comparative research approach seeks to draw parallels and contrasts between two similar or competing systems of thought, among several cultures or within cross-cultural societies. Comparative research methodology is carried out by using a variety of tools, including surveys, personal observation and analysis of national data. Comparative research is useful for classifying shared social phenomena, placing cultural values in context and analyzing cultural differences. A doctoral project in criminal law could use comparative research, for example, to study how various countries in the European Union approach the rehabilitation of convicted criminals.

Clinical Trials

In the field of medicine and biological sciences, clinical trials are the methodology of choice. They are laboratory experiments carried out to test, confirm or disprove scientific theories or to measure the effect of medication or treatment on animals or humans. Clinical trials are conducted by observing the response of certain individuals to medical interventions and comparing those responses to individuals who have not received such medical interventions. In doctoral research in the field of physical therapy, clinical trials are an effective methodology for gauging the effects of therapeutic devices in patients.