Mixed methods research is becoming increasingly articulated, attached to research practice, and recognized as the third major research approach or research paradigm, along with qualitative research and quantitative research. Inquiry and investigation about problems of an interdisciplinary and multidisciplinary domain, such as library and information science studies require decision to be taken about an appropriate research design. In making such a decision, the researcher must tacitly assume a philosophical point of view or a research paradigm. There are four research paradigms which construct the basis of the selection of research methodology and research methods designs. These paradigms include: a) positivism, b) interpretivism, c) critical theory, and d) post-structuralism (Bazargan, 2007). Positivism is the basis of quantitative research method, and of the qualitative research methods are the three paradigms mentioned above (namely; interpretivism, critical theory, and post-structuralism). Because of the nature and complexity of problems in library and information science settings and also the newly matters evolved in this multidisciplinary field, such as information technologies, digital libraries and so on, neither of the quantitative nor qualitative research methods, alone, are able to investigate problems pertaining to them thoroughly. Therefore, researchers of this domain require have a shift toward applying a combination of quantitative and qualitative research methods designs that is named mixed methods research. In this article, first of all we concisely review the philosophical point of views (paradigms) which construct the basis of research methods. Thereafter history and the characteristics of mixed methods research will be reviewed. Finally, applications of mixed methods research in the library and information science (LIS) are discussed.
