Introduction: One of the main pillars of the study is the correct choice of study design. This study aimed to give an overview of different type of study designs in medical research. Methods: In this tutorial study, all applied research designs in terms of quantitative and qualitative study were reviewed. Accordingly, terms related to "Research Designs" were searched in the online databases such as Google Scholar, PubMed, Web of Science and Scopus. Results: Based on the findings of the present study, the types of studies are generally divided into two groups: quantitative studies and qualitative studies. Quantitative studies are divided into two categories: primary and secondary studies. Preliminary studies include observational and non-observational studies. Observational studies are divided into two categories: descriptive and analytical studies. Descriptive studies include case reports, cross-sectional studies, cross-sectional correlational studies and ecological studies, and analytical studies include retrospective and group studies. Non-observational studies also include laboratory studies, clinical trials, field trials, and community trials. Conclusion: With a good understanding of the types of studies, it is easy to decide which type of study is appropriate for the research. Choosing proper study design can reduce the costs of the executive process, increase the accuracy, quality of research and give more reliable results.

Introduction: One of the main pillars of the study is the correct choice of study design. This study aimed to give an overview of different type of study designs in medical research. Methods: In this tutorial study, all applied research designs in terms of quantitative and qualitative study were reviewed. Accordingly, terms related to "Research Designs" were searched in the online databases such as Google Scholar, PubMed, Web of Science and Scopus. Results: Based on the findings of the present study, the types of studies are generally divided into two groups: quantitative studies and qualitative studies. Quantitative studies are divided into two categories: primary and secondary studies. Preliminary studies include observational and non-observational studies. Observational studies are divided into two categories: descriptive and analytical studies. Descriptive studies include case reports, cross-sectional studies, cross-sectional correlational studies and ecological studies, and analytical studies include retrospective and group studies. Non-observational studies also include laboratory studies, clinical trials, field trials, and community trials. Conclusion: With a good understanding of the types of studies, it is easy to decide which type of study is appropriate for the research. Choosing proper study design can reduce the costs of the executive process, increase the accuracy, quality of research and give more reliable results.

Over the past decade, mixed methods research has gained particular attention in social and behavioral research as a considerable number of studies investigated theoretical and methodological aspects of conducting mixed methods research. In applied linguistics, however, mixed methods research is a new approach and little research exists on theoretical and methodological issues related to mixed-method designs. The present study has explored the research designs in which qualitative and quantitative components were combined in the field of applied linguistics. A qualitative analysis of 205 research articles published in seven peer reviewed applied linguistics journals over a period of 14 years revealed that two major categories of mixed-method designs were used in the studies (i.e., sequential and concurrent). Also, subcategories similar to those used in social research emerged in a good number of studies (i.e., triangulation, embedded designs, exploratory designs, explanatory designs). However, the findings further indicated that applied linguistics researchers did not draw on the previously known designs from social research and adopted a pragmatic approach to integrating qualitative and quantitative strands. The findings of this study may help us develop an enhanced understanding of how mixing can be systematically utilized in applied linguistics research.