Now the other options, you might say, well, is this maybe an observational study? And remember, an observational study, observational, that's more of where you look at a population, you look at a group, you ask them a bunch of questions often, or you make a bunch of observations, and you see if there's correlations between two variables. So variable one and variable two, and you're able to make some type of correlational statement. And you're not trying to get at causality. And in a sample study, a sample study, this is just you trying to estimate a parameter for the entire population. So a sample study might have been of the entire population, what percentage gets migraines? And you can't talk to the entire population, maybe the entire population is millions of people, so you take a sample of, say, 100 people, and you ask them, do you get migraines?