My research papeer involved both qualitative and quantitative method and I need to select the sample for them and so I try separate among those methods.
The approaches you use for sampling will depend on your research goals and research design. So, can you tell us more about study?
Assuming you have adopted mixed methods research (MMR), you could follow the six considerations elaborated by Onwuegbuzie and Collins (2017) for proper sampling in an MMR study, bearing in mind the typology they detailed in their earlier article (see Onwuegbuzie & Collins, 2015). Here are the full citations to their works.
Onwuegbuzie, A., & Collins, K. (2015). A typology of mixed methods sampling designs in social science research. The Qualitative Report. https://doi.org/10.46743/2160-3715/2007.1638
Onwuegbuzie, A., & Collins, K. (2017). The role of sampling in mixed methods-research. KZfSS Kölner Zeitschrift für Soziologie und Sozialpsychologie, 69(S2), 133-156. https://doi.org/10.1007/s11577-017-0455-0
Good luck,
I diid a little more digging and found this article, which has over 6,000 citations in Google Scholar.
Teddlie & Yu (2007). Mixed methods sampling: A typology with examples. Journal of Mixed Methods Research. 1 (1), 77-100.