As part of my research I have conducted two survey questionnaires where the first one has closed ended questions and the second one has both closed and open ended questions. My doubt was whether to call this a Quantitative or Mixed Methods approach?
It depends on how you use the open-ended questions. For example, if you convert them to dummy variables according to what was or was not mentioned, then the overall project would remain quantitative. Alternatively, if you use that data to interpret the quantitative results, this could be a sequential explanatory ( QUAN --> qual) mixed methods design.
Agreed. Because the first survey which has closed ended questions is only to check if the participant is eligible and has the knowledge to participate in the second survey which has open ended questions. So this can be considered as sequential explanatory mixed methods design.
I had a follow up question to this. If I am using descriptive statistics to analyse quantitative findings and thematic analysis to analyse qualitative findings, then which would be the method for integration?
It is often difficult to integrate designs that are QUAN + QUAL, unless there is considerable overlap in the content of the two datasets. This is one reason why it is often preferable to use a sequential explanatory ( QUAN --> qual) mixed methods design. In that case, you establish something in the quantitative portion of the research, which you pursue further in the qualitative portion.