Then any statistics you measure on that population might be fully accurate for those 100 but might be less able to predict what the next 100 will look like.
You can still measure stats with smaller groups, it just means the confidence interval is smaller. With 300, there’s a 95% chance your test results are close to reality. With 100 it might be more like 66%.
That doesn’t make sense. What if your population is only 100?
Then any statistics you measure on that population might be fully accurate for those 100 but might be less able to predict what the next 100 will look like.
You can still measure stats with smaller groups, it just means the confidence interval is smaller. With 300, there’s a 95% chance your test results are close to reality. With 100 it might be more like 66%.