Though you have given us very little context. It is reasonable to assume that the experiment is performed on a sample taken from a particular population of interest (e.g. people suffering from a particular medical condition, people with particular habits (e.g. smoking), exposed to a particular substance or within a certain age-range). The phrase "of interest" means that this does not refer to just everyone/people in general.

The validity of research results depends upon whether they can be used to extrapolate from the sample population to the whole of that particular population. That will be governed by how well the sample was randomised etc. and the quality of the experiment.