Your reflection clearly contrasts the strengths of quantitative and qualitative approaches, and your idea to use follow-up interviews after regression is a solid ...
Your reflection clearly contrasts the strengths of quantitative and qualitative approaches, and your idea to use follow-up interviews after regression is a solid mixed-methods strategy. To make it even stronger, specify which variables from your study (e.g., mastery, stress, or PCOISS) you would explore qualitatively, and name the design—such as an explanatory sequential design. Also, briefly mention how you would select interview participants (e.g., high vs. low stress groups) to show intentional sampling. Overall, your reasoning is sound; adding these concrete details will elevate your proposal.