It depends on whether you are using an equal priority design (QUAL + QUAN). If so, then the qualitative portion of your project should be able to stand on its, which would require the use of standard practices such as saturation.

For the qualitative component in a convergent parallel mixed methods design, you could employ purposive sampling, intentionally selecting participants who possess relevant characteristics or experiences related to the investigation topic. Besides, you could utilize the saturation criterion for judging when to stop sampling. This approach ensures that the collected qualitative data is rich and meaningful, providing in-depth insights and understanding to complement the quantitative findings. The following article might be of interest.

Onwuegbuzie, A. J., & Collins, K. M. T. (2017). The role of sampling in mixed methods-research: Enhancing inference quality. KZfSS Kölner Zeitschrift Für Soziologie Und Sozialpsychologie, 69(S2), 133–156. https://doi.org/10.1007/s11577-017-0455-0

Good luck,

Thank you for the reference to Onwuegbuzie, A. J., & Collins, K. M. T. (2017).