Comparative Research: An Old Yet Unfamiliar Method

Comparative research is the study of similarities and differences between two or more cases (1). The history of comparative research methods can be traced back to ancient Greece (2). The present popularity of this research design is due to globalization and higher awareness of socio-cultural differences (2). Although comparative studies are widely used in different disciplines, such as philosophy, anthropology, sociology, law, education, politics, and health; there is a small number of texts on the principles and methodology of this research design (1–4).

In doing comparative research, researchers compare a particular issue within different contexts through quantitative or qualitative approaches (5,6). Comparisons are carried out on different levels including regional, national, or wider geographical boundaries based on specific subjects or areas of interest. There are various types of comparative studies in regard to the context, including but not limited to cross-cultural, cross-national, cross-system, or cross-institutional (1,5). It is also possible to compare a single context through different time frames (6).

The goal of comparative research is to describe, explore and explain the similarities and differences of the cases under study. Conducting comparative research expands one's knowledge and understanding of their own culture, country, or system and those of others. Testing a theory across diverse settings, learning from policy initiatives of others, improving the international understanding of a particular issue, identifying marginalized cultural forms, and evaluating the scope and value of certain phenomena are amongst the aims of comparative research, and it is up to the researcher to identify which of these aims they are targeting for (1,3,5). Indeed, results of comparative studies lead to discovering the knowledge gap and opening new directions and opportunities for future research about issues that researchers may not have been aware of, beforehand (5). Comparative research in the health sciences helps finding solutions and making decisions that will improve the health-related issues. Also, it provides a chance to adopt more effective and/or new practices, procedures, or guidelines from other contexts (1).

There are multiple approaches for data collection in comparative research, which must be chosen based on the research question and whether the research has a quantitative or qualitative approach. Researchers can use a variety of data sources, which are categorized into two groups: primary and secondary data. While primary data can be gathered by observations, questionnaires, surveys, interviews, scales, and measurements; secondary data is existing data that can be accessed through databases, publications, and censuses among other ways (1).

The comparative process in most comparative research consists of five operations, which are not necessarily linear and/or sequential. Selection of cases, description of chosen items from cases based on their context, juxtaposition or observing and analyzing similarities and differences of the selected cases, redescription or "description" based on information gained through juxtaposition, and finally rectification, which is revision and redefinition of the categories involved in the study (7). To analyze comparative research, quantitative or qualitative approaches can be used (1,4). In order to analysis quantitative data one may use statistical methods such as comparing means, factor analysis, cluster analysis, or regression methods. For qualitative comparative analysis, there can be four approaches, based on the research question: descriptive, basic explanatory, comparison of relation, and comparative explanatory (4). Descriptive approach is the simplest type and deal with the extent that a phenomenon occurs across different cases. The basic explanatory approach addresses how characteristics of the units can explain differences in some kind of output variables within each unit. The third type, comparison of relation, focuses on the relationship that exists between an independent and a dependent variable and whether this relationship is similar in different contexts. The most challenging approach is comparative explanatory, which focuses on explaining variation in relations across units (8). Like other research methods, comparative research face obstacles and limitations. Language is one of the most important barriers in comparative studies, i. e. the meaning of particular terms may be lost in the translation of data, and also the same term may have different meanings in different contexts. The language barrier can also affect the validity of data collection tools like questionnaires (5). Additionally, synchronizing a study design and processing it in different contexts can be very challenging, time consuming and expensive (1,4,7). In most published comparative studies, the subject under study is only described in each context without a real comparison and/or exploration taking place, so it is often left to the reader to do the actual comparison (3,6). Another obstacle is that most studies categorized as comparative, lack the theoretical underpinning of comparative study and/or lack logical case selection process (4,5). Case selection is important and crucial and at the same time very challenging. The research questions and aims must guide case selection. Choosing too similar or too different cases makes the comparison challenging (3).

To sum up, comparative research employs quantitative or qualitative approaches aiming to identify, analyze and explain similarities and differences across contexts. Even though comparative research is challenging, it is rewarding at the same time. The understanding and knowledge that can be achieved through comparative research of different contexts and cultures is barely reached by other approaches.

Conflicts of interest

Authors declared no conflicts of interest.