articipants to study Hypertension and the benefit of self-management of diabetes; How to justify why I chose 65 and not select 50 or 100 participants?...

For a nursing research in 3 clinics, I chose 75 participants to study Hypertension and the benefit of self-management of diabetes; How to justify why I chose 65 and not select 50 or 100 participants?

Thank you