Assessing sample vs. "assessing population" Suppose I have a group of people I want to know more about, i.e. my population. It consists of 100 people. I could take a proper subset of it, say 10 people, and survey them. Instead, I survey all of them (100).
My question is: am I assessing a sample or the population itself?
Is "assessing the population" even correct to say, or is it that every assessment I make necessarily takes a sample as subject?
 A: It will depend on what you truly consider the population.
If you only are interested in those 100 people and don’t want to try to make inferences about other people or situations, then those 100 people form a population. You no longer use inferential statistics like hypothesis testing and confidence intervals. Instead of hypothesis testing if the mean is significantly different from zero, you have the whole population. If you calculate a mean that is different from zero, the mean is different from zero with 100% certainty.
That would be the exception in statistics. Usually you’d want to use information about those 100 people to say something about a larger population. That population can be ethereal. For instance, if you want to know if people in 2019 are on average taller than people were in 1919, you perhaps could measure all heights of people today, and say that you have all heights of people 100 years ago. If you posit that better nutrition (for instance) has allowed for taller heights, then probably what interests you isn’t the heights of people but the process that generates people. Existing people are the random sample of the sperms that got there first, but it just as easily could have been a different one.
(There are flaws with this exact example once you think about it a bit. However, I think it illustrates the point of why you might sample all people yet still want to do inferential statistics.)
