If you are worried that your sample will be too small, consider:
- Broadening the variable categories you have applied to your study population (such as a wider age range)
- Determining whether you can remove an exclusion criterion or comorbidity to analyze separately while still maintaining the integrity of the research question, scope of the project, and the scientific value
- Expanding the study population to nearby hospitals through a proxy IRB process
- Utilizing data from national databases