You should read more about statistical significance. Under some reasonable assumptions, you can confidently certain deduce things with small sample sizes. From

You should read more about statistical significance. Under some reasonable assumptions, you can confidently certain deduce things with small sample sizes. From another perspective: we've deduced a lot of things about how atoms work without any given experiment inspecting more than an insignificant fraction of all atoms. TL;DR: The population size (25e6 total devs, 1e80 atoms in observable universe) is almost entirely irrelevant to hypothesis testing.