Creswell (2009) stated that mixed-methods research is an approach to inquiry that involves philosophical assumptions, and the use of qualitative and quantitative approaches in a study. With that being said:
Is it possible to have a well rounded qualitative-inclusive study?
Is it possible to have an informative quantitative-inclusive study?
Triangulation is also, the main advantage of using Mixed Method. However, you can achieve triangulation with qualitative as well...how?
Creswell, J.W. (2009). Research design: Qualitative, quantitative, and mixed-methods approaches. Thousand Oaks, California: SAGE Publications, Inc.
Yes, it is possible in both cases. When there is a study done, as long as the reliability and validity of the research is sound, the study is considered well rounded. For a quantitative study, a literature review, a description of the question and the problem and then a fair testing of valid data can give one the answers ...
The solution discusses the advantage of using triangulation in a mixed method.