The phrase "study population" refers to a group of people who are the focus of research or study. It includes the individuals that are being examined or observed to gather information and draw conclusions. Full definition
For the most part, intervention effects have not proven to be significantly different for different types of study populations. (child-encyclopedia.com)
The most common study populations for these newer drugs are patients with chronic low back pain. (sciencedaily.com)
We acknowledge that replication of our findings in larger study populations is required because the sample size is small. (journals.plos.org)