Q Methodology is a research method used in psychology and in social sciences to study people's "subjectivity"—that is, their viewpoint. Q was developed by psychologist William Stephenson. It has been used both in clinical settings for assessing a patient's progress over time (intra-rater comparison), as well as in research settings to examine how people think about a topic (inter-rater comparisons).
The name "Q" comes from the form of factor analysis that is used to analyze the data. Normal factor analysis, called "R method," involves finding correlations between variables (say, height and age) across a sample of subjects. Q, on the other hand, looks for correlations between subjects across a sample of variables. Q factor analysis reduces the many individual viewpoints of the subjects down to a few "factors," which are claimed to represent shared ways of thinking. It is sometimes said that Q factor analysis is R factor analysis with the data table turned sideways. While helpful as a heuristic for understanding Q, this explanation may be misleading, as most Q methodologists argue that for mathematical reasons no one data matrix would be suitable for analysis with both Q and R.
The data for Q factor analysis come from a series of "Q sorts" performed by one or more subjects. A Q sort is a ranking of variables—typically presented as statements printed on small cards—according to some "condition of instruction." For example, in a Q study of people's views of a celebrity, a subject might be given statements like "He is a deeply religious man" and "He is a liar," and asked to sort them from "most like how I think about this celebrity" to "least like how I think about this celebrity." The use of ranking, rather than asking subjects to rate their agreement with statements individually, is meant to capture the idea that people think about ideas in relation to other ideas, rather than in isolation.
The sample of statements for a Q sort is drawn from and claimed to be representative of a "concourse"—the sum of all things people say or think about the issue being investigated. Since concourses do not have clear membership lists (as would be the case in the population of subjects), statements cannot be drawn randomly so they do not meet R methodology expectations for statistically valid inferences. Commonly Q methodologists use a structured sampling approach in order to try and represent the full breadth of the concourse.
One salient difference between Q and other social science research methodologies, such as surveys, is that it typically uses many fewer subjects. This can be a strength, as Q is sometimes used with a single subject, and it makes research far less expensive. In such cases, a person will rank the same set of statements under different conditions of instruction. For example, someone might be given a set of statements about personality traits and then asked to rank them according to how well they describe herself, her ideal self, her father, her mother, etc. Working with a single individual is particularly relevant in the study of how an individual's rankings change over time and this was the first use of Q-methodology.
In studies of intelligence, Q factor analysis can generate Consensus based assessment (CBA) scores as direct measures. Alternatively, the unit of measurement of a person in this context is his factor loading for a Q-sort he or she performs. Factors represent norms with respect to schemata. The individual who gains the highest factor loading on an Operant factor is the person most able to conceive the norm for the factor. What the norm means is a matter, always, for conjecture and refutation (Popper). It may be indicative of the wisest solution, or the most responsible, the most important, or an optimized-balanced solution. These are all matters for future determination.
An alternative method that determines the similarity among subjects somewhat like Q methodology, as well as the cultural "truth" of the statements used in the test, is Cultural Consensus Theory.
The "Q sort" data collection procedure is traditionally done using a paper template and the sample of statements or other stimuli printed on individual cards. However, there are also computer software applications for conducting online Q sorts. For example, consulting firm Davis Brand Capital has created a proprietary online product,nQue, that they use to conduct online Q sorts that mimic the analog, paper-based sorting procedure. However, the web-based software application that uses a drag-and-drop, graphical user interface to assist researchers is not available for commercial sale. UC Riverside's Riverside Situational Q-sort (RSQ), a newly developed tool by the university, purports to measure the psychological properties of situations. Their International Situations Project is using the tool to explore the psychologically salient aspects of situations and how those aspects may differ across cultures with this university-developed web-based application.
Q-methodology has been used as a research tool in a wide variety of disciplines including nursing, veterinary medicine, public health, transportation, education, rural sociology, hydrology and mobile communication. The methodology is particularly useful when researchers wish to understand and describe the variety of subjective viewpoints on an issue.
Some information on validation of the method is available. The retrospective process using the methodology for any researches needs to be taken. Serious doubts have been raised with respect to the validity of Q-methodology when used for inter-rater comparisons. 
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- Gerard Keegan Webpage about Q Methodology
- Q Methodology news Includes the latest news on Q, including courses and conferences.
- Q Methodology page Includes more information on Q, including tutorials, as well as free software for conducting a Q factor analysis.
- Q Methodology tutorial Original instruction materials on Q Methodology.